142 Prof. H. G. Seeley. The Shoulder Girdle 



have the external ascending process elongated rather more than in 

 other specimens. 



The interclavicle appears to have been sub-reniform, but its margin 

 is imperfect all round. Its thin condition is more like that of a 

 clavicle. It is inches wide, and inches deep. It shows radiating 



Fig. 9. — Imperfect interclavicle of Murcenosaurus (sp.). 



lines of growth, and there are no indications of contact with other 

 elements of the clavicular arch. If the bone is correctly determined, 

 it shows an interesting modification of the interclavicle. 



Oxford Clay Elasmosaurians show two types of variation from the 

 kind of clavicular arch now described. One consists in the approxi- 

 mation of the clavicles, so that they articulate, and in this type there 

 is no evidence of an interclavicle. In the other modification the inter- 

 clavicle persists, wedged between the scapulae, and the clavicles are 

 probably not represented, or present as delicate films which have not 

 been perfectly preserved. 



(iv.) The type in which the clavicular arch reaches the smallest 

 dimensions known to me is in the private collection of Mr. A. N". 

 Leeds. Its remains comprise the shoulder girdle, bones of the fore 

 limb, and some cervical vertebrae. A vertebra which is from the 

 middle of the neck, and believed by Mr. Leeds to be about the 15th, 

 has the centrum transversely ovate, If inch wide, 1J inch deep, and 

 1J- inch long. The articular face is slightly concave, and margined 

 by a narrow border. The ribs and neural arch are anchylosed to the 

 centrum. The neural spine is compressed and somewhat elongated 

 rising inches above the base of the centrum. 



The shoulder girdle is perfectly preserved. The least transverse 

 measurement over the articular surfaces for the humerus is under 



