650 RAMSAY S. TRAQTJAIR ON AMBLYPTERTJS, 



success. He showed, however, very clearly that Agassiz's genus 

 Amblyptevus contained at least two very distinct types : — first, 

 that of A. macropierus, in which the scales are striated, and the 

 teeth large and conical, with an outer row of smaller ones, and for 

 which he proposed the new generic term Rhabdolepis ; second, that 

 of A. latus, in which the scales are smooth, and the teeth minute 

 and slender, without interspersed laniaries ; and to this he limited 

 the name Amblypterus, the character of the dentition being more in 

 accordance with the original definition of the genus. A. Agassizii 

 Minister, A. striatus, Ag., and A. ornatus, Giebe], he considered as 

 probably belonging to Rhabdolepis ; while, as regards A. neuronevus 

 and punctatus, Ag., he expressed a suspicion that they might perhaps 

 appertain to new and peculiar genera. Palatal teeth were found 

 by him both in Rhabdolepis and Amblypterus proper ; and this 

 character he thought might possibly serve to separate Amblypterus 

 from Pcdceoniscus on the supposition that they are absent in the 

 latter. The following summaries of characters are given at the con- 

 clusion of his paper : — 



" Rhabdolepis, Troschel. Grosse conische Zahne in einer lieihe in 

 den Kiefern ; hechelformige Gaumenzahne ; Schuppen massig und 

 gestreift. Flossen gross. 



" Amblyptevus, Agass., Troschel. Zahne hechelformige in den 

 Kiefern ; zahlreiche Gaumenzahne. Schuppen massig und glatt. 

 Flossen gross mil kleinen Fulcra. 



" Palceoniscus, Agass. Hechelformige Zahne in den Kiefern. 

 Keine Gaumenzahne? Flossen massig mit deutlichen Fulcra. 

 Schuppen gestreift oder glatt." 



The distinction here drawn between Rhabdolepis and Amblyptevus 

 cannot be gainsaid ; but as regards Palceoniscus it is simply impos- 

 sible to prove the absence of palatal teeth in the large assemblage of 

 species referred to that genus, if, indeed, in any of them, considering 

 the state of preservation in which their heads usually occur. Other 

 characters must then be sought whereon to found a satisfactory 

 diagnosis, or to throw light on the question which naturally arises 

 as to whether the Agassizian Palceoniscus may not, like his 

 Amblyptevus, include more than one generic type. Troschel, indeed, 

 concludes his paper with the observation, "Es ist wahrscheinlich 

 dass nach Analogie mit Amblyptevus, auch die Gattung Palosoniscus 

 in zwei Gattungen gespalten werden muss, je nachdem die Schuppen 

 gestreift oder glatt sind." 



Nevertheless, in a recent work *, Professor J. Y. Carus has again 

 fused together Amblypterus and Rhabdolepis, to which he also adds 

 as synonyms Gyvolepis, Colobodus, and Tholodus. His definitions 

 are as follows : — 



" Amblyptevus, Ag. (incl. Gyvolepis, Ag., Rhabdolepis, Troschel, 

 Colobodus, Kg., Tholodus, H. von Meyer). Schwanz kurz,Flossen gross, 

 vielstrahlig ; unterer Band des Schwanzes mit doppelten Fulcral- 

 reihen. Kohlenformation bis zur Trias. Arten : A. macvoptevus, 

 Ag., u. a. 



* Handbuch der Zoologie, Bd. i. 2te Halfte, p. 591 (Leipzig, 1875). 



