Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/654

554 stitute a new generic type or may be received into any other genus already known. If we now turn to the genus Elonichihys of Giebel, we shall find that that author characterized the fishes (E. Germari, crassidens, and lævis, from the Coal Measures of Weltin, near Halle) which he referred to it, as standing in the middle between Palæoniscus and Amblypterus, allied to the former by their fulcrated fins, and to the latter by the large size of these organs, as well as by the aspect of their thick striated scales, "which remind us of certain Amblypteri." From Palæoniscus, however, he considered them to differ in the want of the "scaly covering on the fins," and from both in the dentition, which consisted of an external series of minute teeth comparable to the "Bürstenzähne" of Amblypterus, between which larger ones of a slender conical shape were seen, "wie ich dieselben weder bei den Palæonisken noch Amblypteren finde." But, unfortunately for this diagnosis, the fins of Palæoniscus are no more covered with scales than those of any other genus belonging to the family, nor are the fulcra wanting in any of the species which have been classed under Amblypterus, and, finally, it has been shown that more than one of Agassiz's "Amblypteri" possess large laniary teeth quite similar to those of Elonichthys. But although Giebel's conceptions of its relationship to other Palæoniscoid forms were thus somewhat imperfect, I have convinced myself, by a careful examination of the type specimens in the museum of the University of Halle, that the genus Elonichthys is quite tenable, and that to it the Amblypterus nemopterus of Agassiz and the other forms referred to above as specially allied to that species are properly referable. Though closely resembling Rhabdolepis, it differs in the absence of the subopercular plate; the operculum is also usually more largely developed; while from Amblypterus, as restricted by Troschel, the dentition and the greater obliquity of the suspensorium are obvious marks of distinction. From Palæoniscus, to which some of the species were referred to by Agassiz, it is distinguished by the large size of the fins, and by the possession of more differentiated laniary teeth in the jaws. Nearly related to Acrolepis, it differs from that genus in the anterior covered area of the scales being reduced to a very narrow margin; but from Pygopterus it is widely separated by the