VERTEBRATA FROM THE NEOCOMIAN OF KANSAS. 71 



Plesiochelys BELVIDERENSIS, sp. nov. 

 Plate 11, figs. 1-8. 



Shell of moderate size, that of the type-specimen consider- 

 ably smaller than that of P. solodiirensis, Rut., anterior costal 

 bones spearhead-shaped, or triaiifjjular, pointed at the distal 

 end, their breadth contained twice or a little more than twice 

 in their length, the articulation for the first marginal bone 

 being relatively much shorter than in P. soloditrcnsis — that is, 

 equal to one-fifth of the length of the costal itself; neural 

 bones narrow and elongate, the posterior lateral articulation 

 for the costal bone much longer than the anterior and nearly 

 straight (at least not distinctly of exteriorly concave outline 

 in the one well-preserved neural of the type-specimen), an- 

 teriorly emarginate, the emargination in the type-neural being 

 ample, deep and trilateral; vertebral isthmus of type-neural 

 expanded beneath the middle of the bone so as to form a 

 thick, nearly rhombic, plate-like structure; upper surface of 

 shell (costal bones) ornamented with delicate vermicular 

 grooving and pitting. 



Measurcmenis. — Length of anterior costal bone 82, its 

 greatest breadth 38; minimum breadth of narrowest preserved 

 costal bone 24, maximum breadth of broadest 40; length of 

 one of the largest costals (nearly entire) 111; length of neural 

 bone 35, greatest breadth of same 24, posterior breadth of 

 same 14; length of a dorsal vertebra 32, anterior breadth of 

 same 23, posterior breadth of same 17 mm. If proi^ortioned 

 to the anterior costal bone as in P. solodurensis, the carapace 

 of the type-specimen would have a length of some 300 milli- 

 meters, or about a foot. 



Occurrence. — The type of this species, consisting of the 

 two figured anterior costal bones, several other more or less 

 complete costals, the figured neural bone, and the figured 

 (in figs. 6 and 7 inverted) vertebra, were f(mnd by the writer 

 with the vertebra of {? Lamna) quinquelatcralis about half 

 a mile south of the railway station at Belvidere, Kansas, at 

 the upper limit of the black shale that constitutes No. 4 of 

 the " Belvidere section." 



