ICHTHYODECTES. 93 



parietal-epiotic crest, which nrc filled with adipose tissue 1 in Chirocentrus (Text-fig. 

 22a, b, v.) ; while they exhibit a large and deep fossa in the middle of the side of 

 the otic region — a feature characteristic of Elopine and Clupeoid fishes but not of 

 Chirocentrus. 



Genus ICHTHYODECTES, Cope. 

 Ichthyodectes, E. D. Cope, Proc. Amer. Phil. Soc, vol. xi, 1871, p. 536. 



Generic Characters. — Teeth hollow, in deep sockets, not compressed to a sharp 

 edge ; those of the maxilla, as also those of the dentary, almost uniform in size, and 

 those of the premaxilla not much enlarged. Successional teeth formed directly 

 beneath the functional teeth, and no foramina on the inner face of the jaw below 

 the alveolar border. No presymphysial bone. Trunk and fins apparently as in 

 Chirocentrus. 



Type Species. — Ichthyodectes ctenodon (Cope, Proc. Amer. Phil. Soc, vol. xi, 

 1871, p. 536, and Vert. Cret. Form. West, 1875, p. 207, pi. xlvi, figs. 1—4), from 

 the Upper Cretaceous (Niobrara Group) of Kansas, U.S.A. 



Remarks. — All the known remains of this genus, especially those from the 

 English Chalk, are fragmentary ; but specimens from Kansas, and a fish apparently 

 of the same genus from Mount Lebanon, display the principal characters of the 

 trunk and fins, which agree closely with the corresponding parts of Chirocentrus. 

 Various isolated pieces of cranium, vertebral column, fins, and scales, may thus be 

 generically determined without much hesitation ; and a few typical fragments, 

 which correspond in size with one or other of the first two English species recorded 

 below, seem to be worthy of special description. These are treated here because 

 they have not yet been found in definite association with the jaws, by means of 

 which alone the species of Ichthyodectes are diagnosed. 



Cranium.- — The occipital portion of a skull represented in PI. XIX, figs. 5, ha, 

 and another incomplete cranium in the British Museum (no. 49810) are essentially 

 identical with the same parts of skulls already described from the Kansas Chalk." 

 The cranium is shown to have been somewhat deeper than broad, with very 

 prominent supraoccipital and epiotic crests. It has indeed the conformation of the 

 cranium of Chirocentrus, as indicated in the accompanying Text-figs. 22 a — n. The 

 large supraoccipital (socc.) is a saddle-shaped bone, overlapped by the frontals 

 anteriorly, and rising behind, where it is extended between the muscles in a 



1 According to a communication made to the author by Dr. W. Gr. Ridewood. 



2 See especially O. P. Hay, " On certain Genera and Species of North American Civtaceous 

 Actinopterous Fishes," Bull. Amer. Mus. Nat. Hist., vol. xix, 1903, p. 57, fig. 42. Also A. Stewart. 

 " Teleosts of the Upper Cretaceous," Univ. Geol. Surv. Kansas, vol. vi, 1901, p. -!!>", pi. xlix. 



