[page] 331

XXI. On some new genera and species of Heteromerous Coleoptera (Helopidæ) from Tierra del Fuego. By CHAS. O. WATERHOUSE.

[Read 3rd November, 1875.]

Most of the insects described in this paper were brought to this country by Mr. Charles Darwin. They were described by my father, many years ago, in a paper on the classification of the Heteromera. By a most unfortunate accident this paper slipped, during its transport to the Entomological Society, from the wrapper in which it was enclosed, and was lost.

The specimens have remained untouched until the present day, and in the following descriptions I have made use of the original dissections made by my father.

The species are five in number, and, although they all approach the genus Helops, they differ so much in structure and appearance that I have deemed it best to propose three new genera for their reception.

They are all apterous, and one of them was found in some numbers in Tierra del Fuego, on the sea-shore, under stones that were covered to some depth at each high tide.

The following are the descriptions:—

Fam. HELOPIDÆ

CHITONISCUS, G. R. Waterhouse, MS.

Mentum very small. Ligula truncate in front, with the angles rounded. Apical joint of the labial palpi sub-cylindrical, small, nearly as long as the two preceding joints taken together. Maxillary palpi with the penultimate joint not longer than broad; the apical joint twice as long as the second, wider at its apex, but not securiform. Mandibles bifid at the apex. Labrum transverse, not emarginate. Head not much narrowed behind the eyes; clypeus distinctly separated from the forehead by a

[page] 332

deeply-impressed line. Scarcely any ridge over the base of the antennæ. Eyes not very prominent. Antennæ moderately long; the second joint cylindrical, a little shorter than the first and more slender; the third, fifth and seventh joints nearly equal, a little shorter than the second; the fourth, sixth and eighth joints a little shorter than the third, fifth and seventh respectively; the ninth, tenth and eleventh gradually becoming a little stouter. Thorax flattened, all the angles rounded; base emarginate. Scutellum transverse, truncate at the apex. Elytra imperfectly covering the abdomen, diverging posteriorly. Legs long; anterior tarsi with the four basal joints (very gradually decreasing) subaqual; basal joint to the posterior tarsus as long as the two following together. Anterior coxæ prominent, the prosternum sunk between them and channelled; intermediate coxæ: somewhat widely separated from each other; the mesosternum truncate in front, transversely excavated between the coxæ; metasternum very short, with a deep central impression; posterior coxæ rather widely separated. Teguments generally soft.

Chitoniscus brevipennis, sp. n.

Piceus, depressus; corpore subtus, femoribusque piceo-testaceis. Capite sat lato, nitido, irregulariter haud crebre punctulato, clypeo piceo-testaceo. Antennis piceis, articulo primo et 9°, 10° et 11° piceo-testaceis, his pubescentibus. Thorace dorsim depressiusculo, nitido, sat crebre subtiliter punctato, longitudine vix latiori, lateribus rotundatis. Scutello piceo-testaceo, subtiliter punctulato. Elytris basi thorace paulo latioribus postice ampliatis, striatis; singulo elytro margine interno arcuato. Abdomine supra nitido, impunctato, subtus subtiliter aciculato-punctato, punctis setiferis. Pactore nitido, impunctato.

Long. 4¼ lin.; lat. 1½—2 lin.

Hab.—Tierra del Fuego. Brit. Mus.

The surface of the elytra is slightly wrinkled, and the striæ (not deeply impressed) are in pairs and not punctured.

This most curious insect (which from the loose manner in which the joints are set reminds one of a Blatta) was found in some numbers by Mr. Darwin on the sea-shore under stones.

[page] 333

HYDROMEDION, gen. nov.

Antennæ long and slender, the third to tenth joints gradually becoming shorter, the tenth being still one-third longer than broad. Elytra covering the abdomen, not diverging at the apex, the internal margins being contiguous nearly to the apex. Prosternum sunk between the coxæ, keeled. Mesosternum completely shelving in front, compressed between the coxæ, which are not much separated. Metasternum short, channelled behind; posterior coxæ not much separated.

The rest as in Chitoniscus.

Hydromedion elongatum, sp. n.

Elongatum, piceo-testaceum, sat nitidum. Capite sat magno, sat crebre subtiliter punctulato. Thorace capite paulo latiori, longitudine vix latiori, sat crebre fortius punctato, leviter convexo, antice omnino rotundato, postice paulo angustato, angulis posticis [plerumque] fere rectis, obtusiusculis. Scutello transverso, basi parce punctulato. Elytris basi thorace paulo latioribus, et 2¾ longioribus, postice ampliatis, sat convexis, fortiter punctato-striatis, interstitiis sat angustatis, leviter convexis, nitidis; singulo elytro ad apicem rotundato. Abdomine subtus parce subtilissime punctulato.

Long. 5 lin.; lat. 2 lin.

Var.—Head more distinctly punctured. Thorax with the sides much rounded, and the posterior angles more obtuse. Mesosternum only slightly keeled between the coxæ; striæ of the elytra less closely punctured.

Hab.—Tierra del Fuego. Brit. Mus.

PARAHELOPS, gen. nov.

Eyes prominent. Antennæ reaching to the shoulders of the elytra: first joint stout, a little longer than broad; second joint the same length as the first but less stout; third joint as long as the two preceding taken together, cylindrical; the fourth scarcely longer than the second; the fifth to tenth gradually becoming shorter, but not perceptibly thicker; the eleventh joint nearly globular, but with a fine point at the apex. Elytra covering the abdomen, the internal margins contiguous, the internal angle slightly rounded. Prosternum flat between the coxæ (which are not very prominent), not produced behind. Mesosternum completely shelving in front, the

[page] 334

part between the coxæ moderately broad and nearly flat. Abdominal process between the coxæ moderately broad, truncate in front. The rest as in Chitoniscus.

The structure of the sterna in this genus most nearly approaches that of Helops striatus, but the mesosternum is shelving in front and not concave. The apical joint of the maxillary palpi is not securiform, &c.

Parahelops pubescens, sp. nov.

Elongatus, piceo-niger, nitidus, parce breviter griseopubescens. Capite crebre distincte punctato; oculis prominentibus. Thorace [plerumque] convexiusculo, sat crebre distincte punctato, capite paulo latiori, latitudine haud longiori, antice posticeque paulo angustatis, lateribus leviter arcuatis, ante angulis (anticis posticisque) leviter incisis. Scutello triangulari, brevi. Elytris basi thorace paululo latioribus, medio paulo ampliatis, convexis, sat fortiter striato-punctatis; interstitiis hand convexis, subseriatim subtiliter punctulatis. Corpore subtus crebre distincte punctato.

Long. 3 1/3 lin.; lat. 1 1/3 lin.

This species varies in a most remarkable manner both in sculpture and form. The thorax is thickly punctured, sometimes moderately strongly, sometimes very delicately; it is sometimes broadest in front, gradually narrowed behind, the sides being nearly straight; sometimes the sides are much rounded, and the thorax is so narrow in front that only the neck of the head can be withdrawn, whereas in other examples the head and eyes can be withdrawn into the thorax; the posterior angles are at times slightly acute, sometimes obliquely truncate. The elytra vary in length, sometimes bluntly rounded at the apex, at others somewhat attenuated; the striæ are sometimes impressed and strongly punctured, at others not impressed and delicately punctured. These differences are certainly not specific, as the two sides of the same specimen are not always quite alike.

Hab.—Tierra del Fuego. Brit. Mus.

Parahelops Darwinii, sp. nov.

Nigro-piceus, nitidus, sat latus, depressiusculus. Capite crebre fortiter punctato; oculis prominentibus; antennis piceis. Thorace capite duplo latiori, longitudine 1/3 latiori, convexiusculo, crebre fortiter punctato, antice omnino ro-

[page] 335

tundato, postice angustato, lateribus rotundatis, angulis posticis fere rotundatis. scutello transverso, brevi. Elytris thorace paululo latioribus, postice paulo ampliatis, leviter convexis, ad suturam depressiusculis, fortiter striatopunctatis, interstitiis parce subtiliter punctulatis. Pectore discrete fortiter punctato. Abdomine subtiliter discrete punctulato. Tarsis obscure testaceis.

Long. 4½ lin.; lat. 2 lin.

Var.—Thorax with the sides very gently emarginate towards the posterior angles, which are in consequence more distinct.

Hab.—Tierra del Fuego; Valparaiso. Brit. Mus.

Parahelops quadricollis, sp. n.

Oblongus, piceo-niger, sat convexus, nitidus, breviter griseo-pubescens. Capite creberrime distincte punctato; oculis prominulis. Thorace parum convexo, creberrime distincte punctato, capite 1/3 latiori, longitudine 1/5 latiori, rnargine antico medio parum producto, angulis anticis rotundatis, lateribus fere parallelis, ante angulos posticos subito parum obliquis, angulis posticis obtusiusculis. Scutello parvo, triangulari. Elytris thorace paulo latioribus, et 2 1/5 longioribus, sat convexis, postice paululo ampliatis, sat fortiter punctato-striatis, interstitiis vexiusculis, subseriatim subtilissime punctulatis. Abdomine crebre distincte punctato.

Long. 3½ lin. ; lat. 1½ lin.

This specics most nearly approaches C. pubescens, and has the same general structure, but it is relatively broader. It is distinguished by its thicker punctuation of the head and thorax, and by the broad form of the latter. The elytra are proportionately less elongate, the shoulders are distinct. The abdomen is less strongly and less thickly punctured than in C. pubescens, and the pubescence is finer. The apex of the antennæ and the tarsi are pitchy.

Var.—Thorax with the sides gently rounded.

Hab.—Falkland Islands (C. Darwin and Thos. Havers, Esqrs.) Brit. Mus.

[page] 336

To complete this paper I subjoin the following species, collected by Dr. Hooker and Mr. T. Havers:—

Hydromedion elongatum, var.

In the British Museum there are three specimens which differ from the species which I have named H. elongatum in being rather smaller, testaceous, relatively shorter, and having the elytra less strongly punctured, the striæ not impressed. These may prove to belong to a distinct species, but I prefer at present considering them a variety of the above named.

Hab.—Straits of Magellan (Dr. Hooker).

Hydromedion variegatum, sp. nov.

Precedenti affine; minus convexum, testaceum, fuscovariegatum, antennis tibiisque fusco-annulatis. Capite post oculos rotundato-singustato. Elytris sat fortiter subseriatim punctatis, marginibus reflexis.

Long. 3¾—4¼ lin.

I am chiefly induced to give this the rank of a species on account of the form of the head. In H. elongatum the head behind the eyes has the sides parallel, so that the eyes do not project; in the present insect the head is contracted behind the eyes so as to leave them prominent. The thorax is less convex, and has the lateral margins distinct. The elytra are relatively shorter, less convex, not strongly punctured, and the margins are gently reflexed. The apical half of each joint of the antennæ and tarsi is fuscous, and the tibiæ are ringed with the same colour.

Hab.—Straits of Magellan (Dr. Hooker and Capt. Ross). Brit. Mus.

Parahelops Haversii, sp. n.

Ovalis, brunneo-testaceus, nitidus, convexiusculus. Capite creberrime subtiliter punctulato; oculis prominentibus. Thorace capite duplo latiori, longitudine ¼ latiori, leviter convexo, creberrime distincte, punctulato, antice posticeque fere recte truncato, angulis rotundatis, lateribus leviter rotundatis, marginibus reflexis. Scutello transverso, crebre punctulato. Elytris thorace paulo

[page] 337

latioribus, medio leviter ampliatis, convexis, fortiter punctato-striatis, interstitiis convexiusculis, levibus; marginibus lateralibus bene reflexis. Corpore subtus subopaco; abdomine creberrime subtiliter punctulato, flavopubescenti.

Long. 3 lin.; lat. 1 2/3 lin.

In general form this species resembles a Necrophilus (Silphidæ), but has the thorax scarcely broader behind than in front. The eyes are very prominent. The shoulders of the elytra are nearly rectangular, but blunt; the striæ are not deeply impressed, are strongly but not very thickly punctured; the margins are reflexed, the reflexed portion gradually narrowing to the apex.

Hab.—Falkland Islands (T. Havers, Esq.). Brit. Mus.