PAL^ONISCUS, GYB.OLEPIS, AND PYGOPTESTJS. 565 



opposite side ; there is no trace of any infraclavicular, so constant 

 and prominent an element in the shoulder-girdle of all the 

 Palaeoniscidae. 



The scales of the body are smooth ; and those of the flank remind 

 us, in their form, more of the scales of Pholidophorus than of 

 Palceoniscus. 



These details render it sufficiently evident that the fishes entitled, 

 by Mr. Kirkby, Palceoniscus varians, Abbsii, and alius belong 

 neither to the genus Palceoniscus, nor even to the family of 

 PalaBoniscidae. The differences of structure between them and all 

 the other genera which may be included in the last-named family 

 are, indeed, so strong that I am a little surprised to find him 

 comparing Palceoniscus varians with such forms as P. Voltzii, 

 angustus, and wratislaviensis — species which, if they cannot be 

 included in the genus Palceoniscus as now restricted, most obviously 

 belong to the Pakeoniscidoe. Palceoniscus fultus and P. glaphyrus 

 are also mentioned as allied, especially the latter ; and here I am 

 able most fully to agree with the author ; for P. glaphyrus seems, 

 indeed, to be closely related to, if not generically identical with, the 

 little fishes in question. But if that be the case, then it also, as 

 already mentioned, must cease to be regarded as having even family 

 relations with Palceoniscus. But, as regards Palceoniscus fultus, Mr. 

 Kirkby seems to have overlooked the fact that as far back as 1847 

 it was transferred by Sir Philip Grey-Egerton to a new genus, 

 namely Ischypterus ; and I have above shown how widely this genus 

 differs from the Pakeoniscidge in most essential points of structure. 

 It is, in fact, not the type of Palceoniscus, but that of Lepidotus and 

 its allies, which rises before the mind on the contemplation of the 

 structural details of these fishes along with their entire aspect. 

 And it is precisely with this American genus Ischypterus that Mr. 

 Kirkby's fishes display the greatest possible affinity — in the struc- 

 ture of the tail, of the fins, and in the osteology of the head, so far 

 as that can be made out in the genus just named. A difference of 

 decided generic value, however, is to be found in the absence, in the 

 Eulwell-Hill fishes, of the median row of spur-shaped scales along 

 the back, so prominent in Ischypterus ; and in reference to this dis- 

 tinction, I propose the new generic term Acentrophorus for the 

 Palceoniscus varians, Abbsii, and alius of Kirkby. Whether or not 

 Palceoniscus glaphyrus of Agassiz is also inclusible in this genus, can 

 only, as aforesaid, be accurately determined by a reexamination of 

 the type specimen ; but that it also is not related to the PalcBonisci is 

 meanwhile pretty clear to my mind. 



VII. Type of Palceoniscus catopterus, Ag. (? Genus Dictyopyge, 

 Egerton). This little species, from the Triassic Eed Sandstone 

 of Phone Hill, co. Tyrone, was originally named by Agassiz, but 

 was not described by him. Sir Charles Lyell, however, in referring 

 to it in connexion with certain American Triassic forms, says 

 concerning it : — " The Irish Palceoniscus catopterus of Poan or Phone 

 Hill, referred by Col. Portlock to the Trias, is a true Palceoniscus, 

 and not allied generically either to the Ischypterus of Egerton or the 



