70 



it. ill tlie Eiiglisli formations, some ot" which he reil'is to tlirce additional 

 genera, under the names of Cijmhomurus, Erclmusaurus, and Murcenosaurus. 

 Allied species, including a Polycotylus, have also been described by Mr. Hector, 

 from corresponding strata in New Zealand. 



POLYCOTYLUS, Cope. 



This genus is establislied on a series of vertebrae, witli portions of pelvic 

 arch and posterior extremity, discovered in the upper Cretaceous of Kansas 

 by W. E. Webb, superintendent of the land-office in Topeka, Kansas. The 

 point at which the remains were found is about five miles west of Fort 

 Wallace, on the plains near Smoky Hill River, Kansas, in a yellow Cretaceous 

 limestone. 



There are wholes or portions of twenty-one vertebrse, of which but two 

 retain their neural arches, and six are represented by neural arches only. Four 

 centra may be referred to the caudal series, the remainder to the dorsal ; only 

 two indicate the characters of the cervical vertebrae. All of these verteljrse, 

 except the distal caudals, are remarkable for their short antero-posterior diame- 

 ter, and deeply concave, articular faces. This concavity is not, however, of 

 an open, conic form, as in Ichthyosaurus, but is flattened at the fundus, thus 

 exhibiting a small, slightly disciform area. The usual pair of venous foramina 

 appears on the under side of the centrum. The neural arch is continuous 

 ■with the latter, and exhibits no trace of connecting suture. The diapophyses 

 arise from the neural arch in all the dorsals; they are compressed and verti- 

 cal in section. The arch is, of course, narrow antero-posteriorly, and presents 

 a pair of moderately prominent zygapophyses in each direction; the posterior, 

 as usual, articulating downward, the anterior upward. On some of the verte- 

 brae they become closely approximated. The neural spines arc narrow antero- 

 posteriorly, and much stouter transversely than in Elasmosaurus ; they are 

 strongly grooved at the base, both anteriorly, and most so posteriorly. 



The caudal vertebrae are anteriorly quite as large as the dorsals. Two 

 anterior caudals present, on the latero-inferior part of the posterior margin, 

 a pair of widely-se^jarated articular surfiices for chevron-bones. A portion of 

 one of the latter remains ; it is narrow and subcylindric at the base. The 

 diapophyses are situated on the upper part of tlie centrum, and are continuous 

 with it, and without trace of suture. There are two distal cervicals, which 

 are much smaller than the preceding. They are solidly coossified, and have 



