[page] 281

XLIII.—Description of a new genus of Carabideous Insects brought from the Falkland Islands by Charles Darwin, Esq. By G. R. WATERHOUSE, Esq., Assistant Secretary and Curator to the Zoological Society, &c.

Section GEODEPHAGA.
Fam. FERONIIDÆ.

LISSOPTERUS*, nov. gen.

Corpus depressum, elongatum; lateribus elytrorum subparallelis.

Labrum transversum, antice emarginatum.

Labium profunde emarginatum, dente in medio paulo producto, ad apicem truncato.

Palpi filiformes, articulo ultimo ad apicem truncato.

Mandibulæ mediocres, edentulæ, acutæ.

Antennæ mediocres, articulis subæqualibus.

Pedes mediocres; tibiæ anteriores in meribus incrassatæ, et tarsi articulis quatuor dilatati.

This genus is founded upon an insect discovered by Mr. Dar-

* Αισσδç smooth, and πτεζδν, in allusion to the almost total absence of sculpturing on the elytra.

[page] 282

win in the Falkland Islands. Some of the specimens were found in the month of March under a dead bird on the sea-coast in E. Falkland Island. Both by myself and Mr. Darwin this insect was upon a cursory inspection supposed to be a species of Sphodrus, but upon examination it was found to exhibit characters which separate it from that and other published genera. The more conspicuous are, the swollen anterior tibiæ of the male; the femora are also stouter in this sex, and the four basal joints of the anterior tarsi are dilated, and (with the exception of the basal joint, which is triangular,) they are broader than long. The antennæ do not exhibit the short second and long third joint as in Sphodrus, but have the joints all nearly equal in length, the second joint being scarcely shorter than the third, which is not longer than the following joints. In size the present insect is about equal to the Omaseus melanurus, and an idea of its proportions may perhaps be best conveyed by comparing the two: the body is more depressed than in O. melanurus, the head is a trifle broader, and the antennæ are more slender; the thorax presents nearly the same outline, but the sides are not rounded quite to the base as in that insect. The elytra also present nearly the some outline, but besides being less convex, they have the reflected margin much broader and more distinct; the legs are nearly of the same proportions; the dilated tarsi of the male are broader, the tibiæ stouter, and the internal emargination much less distinct, and situated nearer to the apex of the tibiæ. The principal specific characters may he thus expressed:—

Lissopterus quadrinotatus. Liss. niger subnitidus; antennis pedibusque piceis, vel rufo-piceis; thorace supra paulo convexo, subquadrato postice angustiore, lateribus indistincte rotundatis, foveis duabus oblongis impresso, medio canaliculato; elytris elongato-ovatis, lateribus subparallelis postice rotundatis, supra subdepressis, lævibus, indistinctissime striatis, notis quatuor rufis ornatis. Long. corp. 6¾—8 lin. ; lat. 0 2/3—3 lin.

Var. β. Elytris immaculatis, pedibus nigris.

Colour black; head and thorax glossy, elytra dull; head rather broad and subdepressed, with a slight transverse groove in front marking the posterior boundary of the clypeus, which is transverse and slightly emarginated in front, where it is of a pitchy hue; two shallow foveæ situated partly on the clypeus and partly on the head; eyes rather small, rounded and convex; labrum and mandibles pitchy; antennæ and palpi pitchy-red. Thorax about one-fourth broader than long; in front but little narrower than the elytra, and behind about one-fifth narrower than in front; the sides slightly rounded, but becoming nearly straight and parallel towards the posterior

[page] 283

angles, which are nearly right angles; the upper surface is but little convex, the reflected lateral margins are rather broad, the dorsal channel moderately distinct, but obliterated near the anterior and posterior margins of the thorax; on each side, behind, are two oblique, long, smooth foveæ, between which is a transverse impression situated at about one-fourth of the distance from the base towards the apex of the thorax—this transverse impression is not strongly marked. Elytra elongate-ovate, above subdepressed, the lateral reflected margins broad and distinct, the surface nearly smooth but exhibiting indistinct striæ, and these are most faintly punctured; two smallish red spots are observable on each elytron near the outer margin, one towards the base of the elytron, and the other on the apical fourth; the legs are pitchy or pitchy-red. Sometimes the red spots on the elytra are obliterated, the legs are nearly black, and the antennæ and palpi are pitchy.

Obs.—As regards one of the characters upon which I found the present genus, I allude to the male sex having four of the joints of the anterior tarsi distinctly dilated, I may call attention to the remark by Dejean in his observations on the Feroniæ, viz. that this group is distinguished from the Harpali by the structure of the intermediate tarsi (i.e. they are not dilated), and by the fourth joint of the anterior tarsus, which is never dilated in the male sex. The genus Lissopterus therefore affords a remarkable exception to a general rule.