1894.1 -^-^^ [Cope. 



The lateral walls of Ihe centra near to the articular faces are marked with 

 strong rather sharp ridges, which are separated by grooves of several 

 times their width. 



Measurements. mm. 



/ anteroposterior 55 



Diameters of an anterior cervical < transverse 44 



' vertical 45 



^anteroposterior 76 



Diameters of a median cervical < transverse 70 



' vertical 65 



^ anteroposterior 78 



Diameters of a posterior cervical } transverse 107 



' vertical 88 



r anteroposterior 74 



Diameters of an anterior dorsal < transverse 96 



' vertical 90 



The specimen was found with that of the EmbapJiias eirculosus at the 

 Big Bend of the ^lissouri in South Dakota, and was presented' to the 

 museum of the Academy of Natural Sciences by Mr. John H. Charles, of 

 Sioux City, la. 



Elasmosaukus sp. 



Prof. N. H. Winchell sent me for examination a portion of the vertebral 

 column of a Plesiosauroid from the Niobrara Cretaceous of Dakota (exact 

 locality not known), which consists of forty-three centra and portions of 

 the arclies and limbs. It is one of the shorter-necked forms of the genus, 

 resembling the E. intermedius in the proportions of its cervical vertebrae. 

 The dorsals are relatively larger, but they are all, with most of the cervi- 

 cals, so distorted by pressure that it is impossible to characterize the 

 species. 



Explanation of Plate. 



Permian and Triassic Cotylosauria and Stegocephali : 



Fig. 1. Mitstodonsaurus giganteus Jaeger ; j\ nat. size ; from the Trias 

 of Germany. From Fraas. 



Fig. 2. Chilonyx rapidens Cope ; ^^3- nat. size ; from the Permian of 

 Texas. 



Fig. 3. Pariotichus inegalops Cope ; nearly nat. size ; from the Permian 

 of Texas. 



Fig. 4. ParUylus cordatus Cope ; nearly half nat. size ; from the Per- 

 mian of Texas. 



Lettering. 



Tab., Ostabulare ; Soc, Supraoccipital ; 8m., Supramastoid ; St., Supra- 

 temporal ; Z., Zygomatic (quadratojugal) ; Pob., Postorbital ; Pof., Post- 

 frontal ; P., Parietal ; F., Frontal ; Pef., Prefrontal ; J., Jugal ; Q., Quad- 

 rate ; L., Lachrymal; Mx., Maxillary; N., Nasal ; P?«a;., Premaxillary, 



PROC. AMER. PHILOS. soc. XXXIII. 144. O. PRINTED MARCH 24, 1894, 



