Stewart.] Cretaceous Fishes. 305 



Kreide von Kansas," in which he described his Tchthyodectes 

 poly microdots. Shortly after this Professor Cope reviewed this 

 paper in the American Naturalist** and claimed that Crook's 

 species is the same as the one already described by him as /. 

 arcuatus. He further states that if it had not been for certain 

 conditions, figures of this species would have been published, a 

 statement which I think means that more characteristic parts 

 would have been figured and described. 



(ope was evidently in doubt about the specimen figured as 

 Ichthyodectes (Portheus) arcuatus, as on plate XLVII of the 

 11 Cretaceous Yertebrata," he refers to it as 'Portheus arcuatus, 

 while on the opposite page, in the explanation of the plate, it is 

 Portheus /arcuatus. Furthermore, on page 220 B of the same 

 work, he refers to these figures of an unknown species of 

 saurodont. Altogether I am inclined to think that Professor 

 Cope's description and figures are for entirely different speci- 

 mens, but the description, so far as it goes, does not seem to 

 differ from the description and figures of /. polymicrodus of 

 (/rook. 



When we take into consideration the fact that Professor Cope 

 was able to recognize his species in Crook's description, and 

 also that this form is so abundant in the chalk of western Kan- 

 sas that it could hardly be missed by a party collecting fossil 

 fishes for any length of time in that locality, I do not think we 

 should hesitate to regard Gillie us (Ichthyodectes) 'polymicrodus 

 Crook as a synonym of (rillicus arcuatus Cope. The characters 

 in which Gillicus Hay differs from Tchthyodectes Cope are 

 enumerated as follows by Professor Hay : ,il " While these forms 

 can by no means belong to Cope's Portheus (Xiphactinus of 

 Leidy), they can hardly belong to the genus Tchthyodectes. In 

 the latter genus the maxilla is long, nearly equal to the distance 

 from the tip of the vomer to the occipital condyle. The gape of 

 the mouth must therefore have been large. In Doctor ('rook's 

 species and related forms the maxilla is short, between one-half 

 and two-thirds the distance referred to above ; hence the gape of 



83. XXVI, p. 942. 



»>4. Amor. Jour. Sci., vol. VI, p. 229. 



