4 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [iVpril 18, 



series of strong ridge-sliaped scales. The specific name given by 

 Agassiz is rugosus, probably in allusion to the rugged character of 

 the cranial bones. 



Genus Pal.eoniscus, Ag. 



This genus embraces a greater number of species than any other 

 of the Heterocerque Lepidoids. Not only in species but in indivi- 

 duals the Falceonisci appear to have been the most numerous of the 

 vertebrate denizens of the waters in which they flourished, associating 

 together in large shoals, and performing no doubt important functions 

 in the then economy of nature, probably by reducing and assimi- 

 lating the superabundant vegetable substances brought within their 

 reach, and again in their turn forming the prey of the Megalichthys, 

 Holojyty chilis, Jcrolepis, Pygopterus, and other voracious sauroid fishes 

 with which they co-existed. x\gassiz has described tM'enty-one species 

 in the 'Poissons Fossiles,' inchxAm^ Palceoniscus fultus, which forms 

 the type of the genus Ischypterus and will be alluded to hereafter. 

 In addition to these he mentions in his ' Tableau General' five others 

 as undescribed, besides the American species P. Agassizii and P. 

 macropterus. 



Pal.eoniscus catoptertjs, Ag. 



Although the discovery of this species in the new red sandstone of 

 the county Tyrone was communicated to the Geological Society by 

 Sir Roderick Murchison so long ago as 1 835 *, yet no description of 

 the fish has yet been published. It was assigned to the genus Palceo- 

 niscus by Agassiz, who very happily noted its most distinctive cha- 

 racter in the specific appellation catopterus. In size it is the smallest, 

 in form the most slender species of the genus. The head is small and 

 more pointed than in other Palceonisci; the eye is placed forward; 

 the mouth appears small ; the operculum is nearly semicircular. 

 The dor so-ventral series of scales are very regular and distinct. The 

 scales themselves are large, and of very uniform size over the whole 

 body. The specimens hitherto found are not in a condition to show 

 the superficial characters of the scales, the impressions of the under 

 sides alone being preserved. The dorsal fin is placed much nearer the 

 tail than in any other species ; in this respect, but in no other, PaJcBO- 

 niscus catopterus resembles the genus Catopterus of Mr. Redfield. 

 The tail is decidedly heterocerque. It is altogether so distinct from 

 all the other Palceonisci, that it is recognizable at first sight. 



Pal^oniscus speciosus, Miinst. 



This is from the Kupferschiefer of Richelsdorf, and was named 

 by Count Miinster. Lord Enniskillen, who had an opportunity of 

 seeing the specimen in the collection of M. Althaus, considers it a 

 good species. It is as long as PalcBoniscus magnus, but not so deep. 



Pal^oniscus ornatus, Miinst. 



This species is followed by a note of interrogation in the ' Tableau 

 General,' and Lord Enniskillen, who also saw this specimen, says he 

 * Pioc. Geol. Soc. vol. ii. p. 206. Portlock, Geol. Mem. p. 468. 



