62 THE UNIVERSITY SCIENCE BULLETIN. 



structure of the pectoral girdle. The characters of the genus 

 Elasmosaurus have been given by the senior author^ as follows: 



"Symphysis of mandibles short; teeth markedly anisodont. Neck with 

 seventy-six true cervical vertebrae and three pectorals, the centra increasing 

 in length to the fifty-eighth, and then decreasing in length to the dorsals, 

 thence nearly uniform in length throughout the dorsal region. Posterior 

 cervicals and dorsals much wider than high, and wider than long; spines 

 wide and not high; zygapophyses weak. Pectoral girdle with large scapulae 

 meeting each other in the middle line. No interclavicular foramen; cora- 

 coids broadly separated posterior to the interglenoid thickening, their pos- 

 terior ends not much dilated. Cervical ribs single headed. Ischia short." 



Of these characters the number of cervicals is doubtless a specific 

 character; the species E. serpentinus has but sixty cervicals. The 

 elongation of the posterior cervicals is undoubtedly a real generic 

 character, and is common to various species. The approximation 

 of the scapulae and absence of the interclavicular foramen, and 

 also, in much probability, of the interclavicle, may or may not be 

 of family value. The European forms referred to this family do 

 not have, so far as published, the broad separation of the cora- 

 coids posteriorly. It is very probable that, when the skulls have 

 been more attentively compared, Cryptocleidus and its allies will 

 be excluded from the family Elasmosauridae. 



That the present genus is distinct from Elasmosaurus is evident. 

 Until its skull and pectoral girdle are known its position in the 

 family is doubtful. The only other long-necked genus with which 

 it can be compared is Leurospondylus Brown,^ recently described. 

 So far as the description and figures of that genus apply to the 

 present material the two genera can not be distinguished. 



The material upon which Ogmodirus is based is represented by 

 the following parts: fifty-one consecutive cervical vertebrae, 

 eighteen caudal vertebrae, humerus, femur, many carpal and 

 phalangeal bones, the right ilium, a part of a pubis, and various 

 fragments of ribs and neural spines. This material was collected 

 in 1909 by Mr. C. Boyce in Cloud county, Kansas, associated 

 with the remains of another plesiosaur, and presented by him to 

 the University of Kansas. Its horizon is probably the Fort Hays 

 limestone of the basal Niobrara, though possibly, but improbably, 

 from the uppermost horizon of the Benton. The species has been 

 named in honor of Mr. H. T. Martin, in appreciation of his long, 



1. Williston, S. W. 1906. North American Plesiosaurs: Elasmosaurus, Cimoliasaurus and 

 Polycotylus. Ame'r. journ. Sci., 4th ser., vol. xxi, No. 123, March, p. 225. 



2 Brown, Barnum. 1913. A New Plesiosaur, Leurospondylus, from the Edmonton Cre- 

 taceous of Alberta. Bull. Amer. Mus. Natl. Hist., vol. xxxii, art. xl, pp. 605-615, figs. 1-7. De- 

 cember. 



