356 Systematic Paleontology 



Cretaceous of various parts of the world. Nine or ten genera, chiefly 

 Turonian and Senonian, have been differentiated, of which the largest is 

 Enchodus, so abundantly represented by fragmentary remains in the 

 Upper Cretaceous of North America. 



Genus ENCHODUS Agassiz 

 [Poissons, Foss., Feuill. 1835, p. 55] 



" Trunk elongate-fusiform, both this and the head laterally compressed. 

 Cranial roof exhibiting a deep median longitudinal depression, its lateral 

 and occipital margins ornamented, like the other external bones, with 

 ridges and tubercles of granoine. Mandible a little prominent, provided 

 with an inner widely-spaced series of large slender teeth, the largest in 

 front, also a marginal series of minute teeth, all nearly or completely 

 solid ; premaxilla in the form of a vertical lamina, deepest in front, taper- 

 ing behind, and with a single spaced series of small teeth; maxilla long 

 and slender, either finely toothed or toothless at the oral border ; palatine 

 thickened and tumid, with only one large tooth fixed at its anterior end ; 

 ectopterygoid robust, with a single spaced series of large slender teeth, 

 gradually diminishing in size backwards; no teeth barbed. Operculum 

 strengthened on the inner side by a ridge extending horizontally back- 

 wards from the point of suspension; branchiostegal rays about 12 to 16 

 in number. Vertebrae 40 to 50 in number, about half being caudal ; the 

 centra at least as long as deep, constricted mesially, and marked with small 

 irregular longitudinal ridges. All except the foremost rays of each fin 

 finely divided distally, but none excessively elongated. No postclavicular 

 plate. Pectoral fins large, pelvic fins much smaller and arising for far- 

 wards; dorsal and anal fins large, neither much longer than deep, the 

 former arising much in advance of the middle point of the trunk, the 

 latter also far forwards ; [a posterior adipose dorsal fin observed in a few 

 well-preserved specimens;] caudal fin forked, with curved fulcral rays 

 and stout, articulated, undivided rays at its base both above and below. 

 Rudimentary dermal scutes, not overlapping, in a single median series 

 between the occiput and the dorsal fin, and along the course of the lateral 



