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sub-families and families, some of which are supposed to have perished at different periods, and some to have endured to the present day.
By looking at the diagram we can see that if many of the extinct forms supposed to be imbedded in the successive formations, were discovered at several points low down in the series, the three existing families on the uppermost line would be rendered less distinct from each other. If, for instance, the genera a 1 , a 5 , a 10 , f 8 , m 3 , m 6 , m 9 , were disinterred, these three families would be so closely linked together that they probably would have to be united into one great family, in nearly the same manner as has occurred with ruminants and pachyderms. Yet he who objected to consider as intermediate the extinct genera, which thus link together the living genera of three families, ... would be partly justified, for they are intermediate, not directly, but only by a long and circuitous course through many widely different forms. If many extinct forms were to be discovered above one of the middle horizontal lines or geological formations— for instance, above No. VI.— but none from beneath this line, then only the two families on the left hand (namely, a 14 , &c., and b 14 , &c.) would have to be united into one family; and the two other families (namely, a 14 to f 14 now including five genera, and o 14 to m 14 ) would yet remain distinct. So again, if the three families formed of eight genera ( a 14 to m 14 ), on the uppermost line, be supposed to differ from each other by half a dozen important characters, then the families which existed at the period marked VI. would certainly have differed from each other by a less number of characters; for they would at this early stage of descent have diverged in a less degree from their common progenitor. Thus it comes that ancient and extinct genera are often in a greater or less degree intermediate in character
sub-families and families, some of which are supposed to have perished at different periods, and some to have endured to the present day.
By looking at the diagram we can see that if many of the extinct forms, supposed to be embedded in the successive formations, were discovered at several points low down in the series, the three existing families on the uppermost line would be rendered less distinct from each other. If, for instance, the genera a 1 , a 5 , a 10 , f 8 , m 3 , m 6 , m 9 , were distinterred, these three families would be so closely linked together that they probably would have to be united into one great family, in nearly the same manner as has occurred with ruminants and certain pachyderms. Yet he who objected to call the extinct genera which thus linked the living genera of three families together, intermediate in character, would be justified, as they are intermediate, not directly, but only by a long and circuitous course through many widely different forms. If many extinct forms were to be discovered above one of the middle horizontal lines or geological formations— for instance, above No. VI.— but none from beneath his line, then only .. two of the families (those on the left hand, .. a 14 , &c., and b 14 , &c.) would have to be united into one; .. and there would remain two families, which would be less distinct from each other than they were before the discovery of the fossils. So again, if the three families formed of eight genera ( a 14, to m 14 ), on the uppermost line, be supposed to differ from each other by half a dozen important characters, then the families which existed at the .. period marked VI. would certainly have differed from each other by a less number of characters; for they would at this early stage of descent .. have .. diverged in a less degree from their common progenitor. .. .. .. .. .. .. .. .. .. .. Thus it comes that ancient and extinct genera are often in some slight degree intermediate in cha- racter