i82 CRETACEOUS AND TERTIARY FISH. 



Crommyodus Cope. 



Crommyodus Cope, Proc. Araer. Philos. Soc. Phila., XI, 1869, p. 243. Type 

 Phacodus irregularis Cope, virtual designation and monotypic. {Phaco- 

 dus preoccupied.) 



Teeth fusiform, irregularly and closely crowded on surface of 

 an elongate semidiscoid bone of possibly hyoid apparatus. Mas- 

 ticatory surface moderately convex. Crown abruptly contracted 

 below into short root, which presents very small orifice for ad- 

 mission of nutrient vessels, etc. Teeth thus somewhat shape of 

 an onion inverted. Pulp cavity large. Superficial layer of crown 

 very thin, its structure not known, but its punctate appearance 

 resembles that of a worn surface of vaso-dentine. 



Cope also! states the successional teeth as very abundant, and 

 closely placed. They appear to rise through the spongy tissue of 

 the bone without reference to any definite line of succession or 

 superposition. Those of the inferior series, visible on under sur- 

 face of bone, have an average larger size than those on upper 

 surface which are in use. A single extinct species. 



Crommyodus irregularis (Cope). 



Phacodus irregularis Cope, Proc. Boston Soc. Nat. Hist., XIV, 1869, p. 33. 



Miocene near Shiloh, Cumberland Co., N. J. 

 Crommyodus irregularis Cope, Proc. Amer. Philos. Soc. Phila., XI, 1869, p. 



243 (reference). 

 Cope, 1. c, XIV, 1875, p. 362 (reference). 



Teeth, though irregularly arranged for short distances in lon- 

 gitudinal lines, transversely ovate, closely packed or with slight 

 intervals. Those at outer and inner margins of bone considerably 

 smaller than median and more rounded. Crown of successional 

 teeth flattened, as well as those in use. Median teeth number 5 

 in one-half inch, and lateral 7 in same length. Surface of root 

 finely striate, striae coarser at point of convergence at orifice of 

 pulp cavity. Crown in many teeth broken away, leaving short 

 conic pulp cavity and its thin walls exposed. Bone convex in 

 transverse direction, descending more gradually on convex mar- 

 gin. Length of bone about 40 mm. (From Cope.) 



