Eastman: Triassic Fishes. 143 



"The scales of (he Hanks arc distinctly serrated on their posterior 

 margins, which serration is traceable nearly to the tail. The scales 

 of the pedicle of the caudal fin are less elongated than in C. gracilis, 

 and rarely extend so far on the upper lobe. In general aspect this 

 fish is less elegant than C. gracilis, although the more prominent orna- 

 mentation of scales renders it an attractive species. 



"I have not seen the publications you allude to, nor can I give any 

 idea as to the age of the beds in which the fish occur. But I think 

 there is every reason to warrant the creation of a new genus to receive 

 the Pala^onisci (so-called). The form of the fins is very remarkable, 

 as observed by Agassiz in his description of P. fultiis; but I have 

 discovered a more important feature in the character of the teeth, 

 which are not en brosse as in the Palaionisci, but more nearly resemble 

 the teeth of Tetragonolepis. If on further examination these char- 

 acters should prove constant, I should propose the name Ischypterus 



for this genus. 



"In great haste, yours, 



"Philip Grey Egerton." 



II. 



"OuLTON Park, Tarporly, Dec. 28th, 1844. 

 " Aly dear Lyell: 



"I find I can do nothing with your American Palaeonisci in conse- 

 quence of my ignorance of what Redfield has already done. I have 

 only got the short paper in the Yale (Silliman's) Journal, from which 

 it is absolutely impossible to identify a single species. The specimens 

 sent me by himself are very imperfect, with the exception of the 

 P. fiiltus of Agassiz, and Catopterus gracilis Redfield. I think you 

 have at least five or six distinct species (besides the Catopteri), and 

 they all agree in the generic characters of the fins, scales, and teeth. 

 The latter are not en brosse as in the true Palceonisci, but are strong 

 and conical, and the oral aperture is considerably smaller. 



"I know little about P. catopterus of Roan Hill,* as my specimen is 

 very indistinct, and Agassiz has not described the species in the P. 

 Fossiles. The specific name is no doubt in consequence of the back- 



4 " Palaeoniscus catopterus" of Roan Hill, Tyrone, Ireland, was afterwards figured 

 by Sir Philip Egerton (1858), and still later was shown by Dr. R. H. Traquair 

 to belong to the genus Dictyopyge. The so-called Chelonichlhys asnmssi is now 

 referred to the Arthrodiran genus Homosleus, and the Scottish C. minor is identical 

 with Asterolepis minor. 



