rOXOCHEI.YID^E. 



171 



FIG. 213 Toxnc helys ser- 

 rijer. One peripheral 

 and part of another. 

 XI. 



lower jaw is much smaller. This surface is triangular, the inner lobe seen in T. latiremis 

 being greatly reduced in T . semper. 



The interorbital space (fig. 212) had a width of 16 mm. where narrowest. The groove on 

 the under surface of the frontals for the olfactory nerve is relatively narrower than in T . 

 latiremis, in which the groove is nearly one-third as wide as the interorbital space; whereas, 



in T. serrifer it is only about one-sixth the width of that space. The 

 anterior borders of the prefrontals are broken away, so that the 

 width of the anterior narial passage can not be determined. It is 

 certain, however, that the nasal cavity itself had the lateral extent 

 that it had in T. latiremis. 



An estimate shows that the length of the skull from the snout to 

 the occipital condyle was about 80 mm. 



Two adjacent peripheral bones are present, probably the left 

 eighth (fig. 213) and the ninth. The eighth is 40 mm. long and 32 

 mm. wide, the ninth 43 mm. long and 32 mm. wide. Each is notcht 

 just behind the widest portion and here the width of the eighth is 25 

 mm., of the ninth 27 mm. The thickness of the inner face is nearly 

 7 mm., and at the hinder end of this face is a pit for a rib. 



The specimens which were referred to this species by Case (Univ. 

 Geol. Surv. Kan., iv, p. 379) are described as T. stenopora. From 

 the latter species T. serrifer differs in having a dentary with an 

 alveolar surface much wider in proportion to its depth, and not beakt 

 at the tip. 



It is evident that the skull (and probably the whole skeleton) of T . serrifer was much larger 

 than that of T. stenopora. This makes it all the more remarkable that the dentary of the 

 former is relatively so short and that the depth of T. stenopora is so great. It seems not im- 

 probable that the carapace and part of the plastron described by Wieland as T '. bauri will 

 prove to belong to the present species. 



Toxochelys brachyrhina Case. 

 Plate 31, fig. i. 



Toxochelys brachyrhinus, CASE, Univ. Geol. Surv. Kansas, iv, 1898, p. 378, pi. Ixxxiv, figs. I, 2. HAY, 

 Bibliog. and Cat. Foss. Vert. N. A., 1902, p. 442; Bull. Amer. Mus. Nat. Hist., xxi, 1905, p. 177. 



The type of this species is a skull, the property of Kansas University, and bearing the 

 number 1 212. Dr. Case's description of it is exceedingly brief. The character which he gives 

 as distinguishing it from T . latiremis is the much blunter snout. Case's fig. I of his plate is 

 three-fourths of the natural size; and, while the form of the skull is shown, the details are not 

 well represented. His fig. 2 is a restoration of the size of nature, but it does not indicate the 

 sutures; likewise it represents the anterior half of the skull as somewhat too broad. 



The skull of this species appears to be distinguish! from that of T. latiremis in being 

 narrower posteriorly in relation to the length and in having a broader snout. Another distin- 

 guishing character seems to be found in the narrower posterior region of the palate. In the 

 case of a large specimen of T. latiremis, 130 mm. from the snout to the occipital condyle, the 

 pterygoid portion of the palate, where narrowest,is 36 mm. wide. In the type of T. brachyrhina, 

 1 17 mm. to the occipital condyle, the palate is only 20 mm. wide. The interorbital space also 

 is relatively narrower than in T. latiremis. In the specimen of the latter referred to, the space 

 between the orbits is 24 mm. wide, in T. brachyrhina, only 19 mm. too great a difference to 

 be due to difference of size alone. 



The following measurements are given of the type specimen: 



Millimeters. 



Length from the snout to the occipital condyle u? 



Length to extremity of supraoccipital bone '34 



Distance between the outer faces of quadrates 9 



Distance between outsides of squamosals 94 



Width at hinder borders of orbits 



Width at front of orbits 5 



