I 01 



Diameters of base of parapophysis < 



I V( 



Cope.] 112 [Feb. 2, 



the middle portion of the surface of the centrum, especially at the middle 

 line below, where it is thickened. A large foramen on each side of the 

 middle line below, and a large one below the parapophysis in the cervical, 

 and below the neurapophysis in the dorsal centra. Some smaller ones on 

 the sides of the dorsals. Surfaces of the centra smooth. Neural canal 

 narrow. 



Measurements. mm. 



/ anteroposterior 45 



Diameters of cervical centrum 1 transverse 85' 



( vertical 76 



Vertical diameter of common base of dia- and parapophysis. 67 



anteroposterior 17 



vertical 86 



{anteroposterior 54 

 transverse 99 

 vertical 95 



Width of neural canal at base 19 



Depth of concavity of centrum 13 



This is a species of large size, though not equal in dimensions to the 

 known species of Elasmosaurus. It was found in the upper Cretaceous 

 bed of the Pierre epoch, at the Big Bend of the Missouri river in South 

 Dakota. It was presented to the Academy of Natural Sciences by Mr. 

 John H. Charles, of Sioux City, together with the remains of Elasmosau- 

 rus below mentioned. I wish to express my sense of the obligation under 

 which Mr. Charles has placed the Academy and myself by his liberality 

 in this and other matters. 



Elasmosaurus intermkdius, sp. nov. 



Established on a series of nineteen vertebrjs of the cervical and 

 anterior dorsal regions of an individual from the Pierre formation of South 

 Dakota. 



The vertebral centra are the shortest known in the genus, approaching 

 the Cimoliasaurus in proportions. The median and anterior cervicals dis- 

 play the compressed form characteristic of Elasmosaurus, although they 

 are shorter than in the three known species of that genus. The posterior 

 median cervical vertebrse are depressed, but the centra of the posterior 

 members of that series are less depressed, and Ihej^ increase in length less 

 rapidly than they do in depth. They are shorter absolutely and relatively 

 than in the E. orientalis Cope, to which this species is most nearly related. 

 In the anterior dorsals the depth exceeds the length of the centrum, while 

 in the E. orientalis the depth is about two-thirds the length. The cervi- 

 cals exhibit an angle of the lateral surface about half way between the 

 diapophysis and neurapophysis. The angle disappears on the anterior 

 dorsals. The superior and inferior outlines of the articular faces are not 

 emarginale or concave medially, which they are in the E. orientalis. 



