176 University of Kansas Geological Survey. 



transverse." As the cervical vertebrae of all the species have 

 the faces "slightly transverse," this character is not good for 

 much. Merriam, 1. c, who believed that he had identified this 

 species, says that it is distinguished from T. dyspelor and T. 

 proriger " by its smaller size, by the more lightly formed bones 

 of the skeleton, and by the shape of the quadrate, which has a 

 somewhat longer suprastapedial process, and a larger stapedial 

 groove, and on the upper, inner angle is not so acute." 



Tylosaurus neppeolicus. 



Liodon nepceolicus Cope, Hayden's Bull. U. S. Geol. Surv. of the Terr., 

 1874, p. 37; Cret. Vert., 177, 271, pi. xxxv, ff. 11-13. 



This was based upon the mandible and parts of the maxilla 

 and premaxilla, the quadrate, a dorsal vertebra, etc. "It is 

 about the same size as T. micromus Marsh, but is much more 

 like the T. proriger in character. As compared with T. micro- 

 mus, this species differs in the much less attenuated prem axil- 

 lary and maxillary bones, the anterior nostril, and absence of 

 facets on the crowns of the teeth ; from T. proriger, in the 

 absence of narrow concave facets on the anterior teeth, and an- 

 terior position of the nostril ; from T. dyspelor, in the less com- 

 pressed or less knife-shaped dental crowns, and totally different 

 form of the condyle of the quadrate. The total length of the 

 jaw was twenty-six inches — the length of the quadrate about 

 three inches and a half." 



The characters given — such as may be valid — are altogether 

 too slight to distinguish the species, and I do not believe that T. 

 nepeeolicus is entitled to recognition. 



There is a very small specimen of a Tylosaurus in the museum 

 collection, which may possibly belong to either this or the pre- 

 ceding species, but I believe that it is only the young of T. pro- 

 riger. The humerus measures but three inches in length, the 

 pubis five. The shape of various bones, especially the pelvic 

 ones, is different from those of the other specimens, and, were 

 one to depend upon such characters, it would be easy to con- 

 struct a species. The bones show much compression ; they 

 were evidently more largely composed of organic matter than 

 are the bones usually — a condition expected of young animals. 



