NEMATOGNATHI. 747 



NEMATOGNATHI. 



.RHINEASTES Cope. 



Proceeds. American Philosophical Society, 1872, p. 486. Annual Report U. S. Qeol. Surrey Terra. 1878 



(1873), 638; supra, p. GO. 



Rhineastes pectinatus Cope. 



Bulletin U. S. Geol. Survey Terrs., I, No. 2, 1874, p. 49. 

 Plate V, fig. 13. 



This catfish is represented by a single specimen, which includes only 

 the inferior view of the head and body anterior to the ventral fins. These 

 exhibit characters similar in many respects to those of Amiurus, Raf, but 

 the introperculum, the only lateral cranial bone visible, displays the dermo- 

 ossified or sculptured surface of the Eocene genus, to which I now refer it. 

 Other characters are those of the same genus. Thus the teeth are brush- 

 like, and there is an inferior limb of the posttemporal bone reaching the 

 basioccipital. The modified vertebral mass is deeply grooved below and 

 gives off the enlarged diapophyses that extend outward and forward to the 

 upper extremity of the clavicle. The patches of teeth are on the premaxil- 

 lary, and are separated by a slight notch at the middle of the front margin. 

 The teeth are minute. The four basihyals and the elongate anterior axial 

 hyal are distinct ; also the ceratohyal with its interlocking median suture. 

 The number of branchiostegal radii is not determinable; three large ones are 

 visible. The mutual sutures of the clavicles and coracoids are interlock- 

 ing, and their inferior surfaces display grooves extending from the notches. 

 The pectoral spine is rather small, and bears a row of recurved hooks on 

 its posterior edge ; there are none on its anterior face. The head is broad, 

 short, and rounded in front, which with the uncinate character of the serra- 

 tion of the pectoral spine, reminds one of the existing genus Noturus. 



As compared with the five species of Rhineastes, described from the 

 Bridger Eocene, the present species is distinguished by the small size, and 

 large uncini of the pectoral spine. 



