PAL2E0XISCFS, GYROLEP1S, ANT) PTGOPTERUS. 553 



The body is rather deep ; the scales and cranial bones striated ; the 

 fins are large, many-rayed ; their fulcra small ; the dorsal is nearly 

 opposite the interval between the ventrals and the anal ; the base 

 of the ventrals is long. The operculum is narrow and pointed 

 below ; a small triangular subopercular plate, whose anterior 

 superior angle is produced upwards in a narrow linear process lying 

 along the anterior margin of the operculum for some distance, is 

 intercalated between the last-named bone and the anterior part of 

 the upper margin of the interoperculum. The laniary teeth are 

 sharp, conical, moderate in size, and pretty closely set, with a series 

 of smaller teeth outside. 



The peculiar characters of the Amhlypterus striatus of Agassiz 

 render necessary the institution for it of a new genus, which I 

 propose to denominate Cosmoptyehius, being in some respects 

 intermediate between ffliabdolepis and Elonichthys, but differing 

 from both in the extended bases of the ventral fins. In the last 

 respect, as well as in the form of some of the bones of the head, it 

 resembles Cheirolepis, though of course differing very widely from 

 that genus in other respects. As yet we are only acquainted with 

 one species of Cosmoptychius, which has been found only in the 

 Lower Carboniferous strata (Calciferous Sandstone series) of the 

 neighbourhood of Edinburgh. 



IY. Type of A. nemopterus (Genus ElonichtJiys, Giebel). The 

 scales are moderate, striated or striato-punctate ; the median fins, 

 and sometimes also the paired fins, are large and many-rayed ; 

 their fulcra small : the rays of the pectoral articulated ; the base of 

 the ventrals not extended ; the dorsal situated nearly opposite the 

 interval between the ventrals and the anal ; the caudal powerful. 

 The suspensorium is very oblique ; there is no subopercular plate 

 intercalcated between the operculum and the interoperculum. 

 There are large conical laniary teeth intermixed with and internal 

 to a series of smaller ones. 



To this type belong the A. nemopterus of Agassiz, and one of the 

 two species which he confounded together under the name of A. 

 punctatus (Poiss. Foss. Atlas, vol. ii. tab. 4 c. figs. 3 and 5). 

 Between these and at least two others referred to Pcdceo?iiscus by 

 Agassiz, viz. P. striolatus, Ag., and P. JRobisoni, Hibbert, it is, 

 as already mentioned, simply impossible to draw any generic dis- 

 tinction. The same must be also said of his " Pygopttrus " Buck- 

 landi, which resembles Pygopterus in hardly anything save its large 

 size. Pcdceoniscus Egertoni, Ag., agrees also very closely, save in the 

 structure of the pectoral fin, in which the principal rays do not 

 commence to be articulated for a little distance from their origin. 

 Of Amhlypterus Portloclii, Egerton, I have only seen fragments ; but, 

 so far as these go, they seem to show that this species belongs to 

 the same type with the others named above, as probably also do 

 Pcdceoniscus Brownii of Jackson and P. peltigerus of Newberry. 



As these fishes can be included in none of the three genera already 

 defined, nor yet in Pedceoniscus, in the sense in which that generic 

 term must now be emploved. it remains to be inquired if thev con- 



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