( 609 ) 



* 



XIX. Apractocleidus teretipes : A new Oxfordian Plesiosaur in the Hunterian 



Museum, Glasgow University. By William R. Smellie, M.A., B.Sc. (With 

 One Plate.) Communicated by Professor J. W. Gregory, D.Sc, F.R.S. 

 Edin. and Lond. 



(MS. received January 15, 1916. Read March 20, 1916. Issued separately August 29, 1916.) 



This Plesiosaur was collected from the Oxford Clay near Peterborough by A.N.Leeds, 

 Esq., F.G.S., and was acquired for the Hunterian Museum, Glasgow University, by 

 Professor J. W. GreCxORY. The major portion of the skeleton is present, and the 

 bones are in an excellent state of preservation. The specimen has many striking 

 resemblances to Cryptocleidus oxoniensis, but detailed examination showed that it 

 could not belong to that species, and the differences existing in the paddle, shoulder- 

 girdle, number of vertebrae, and conditions of ossification are such that it cannot be 

 retained in that genus as now defined. Under the circumstances it seems advisable 

 to create a new genus. A short preliminary account of the specimen has already 

 been published (Smellie, 1915), and from that account the following diagnosis of the 

 genus has been taken : — 



Apractocleidus, gen. nov.* 



Plesiosaurs in which the neck is composed of about twenty-nine vertebrae, of which 

 the centra are wider than high and slightly higher than long. The oval articular 

 ends are concave in the centre but convex near the margin. There are three pectoral 

 vertebrae and twenty-three dorsals, or two pectorals and twenty-four dorsals. The 

 shoulder-girdle is of Elasmosaurian type, and so ossified as to form a very rigid 

 structure. The coracoids are exceptionally broad, and the posterolateral processes 

 are greatly produced. The dorsal rami of the scapulae are widely extended in a 

 similar fashion. The ventral ramus of the scapula is large, and in the adult the 

 anterior portion has grown forward beyond the clavicles, which are very thin films 

 of bone lying wholly within the visceral surface of the scapulae. A rudimentary 

 interclavicle may be present. In the mid-ventral line the scapulae and the anterior 

 parts of the coracoids impart a slightly carinate appearance to the shoulder-girdle. 

 The humerus is greatly expanded distally, and articulates with four elements. The 

 pelvis is of great breadth, and the wide spread of the antero-external angles of the 

 pubes. taken in conjunction with the breadth of the shoulder-girdle, indicates a genus 

 of exceptionally broad build. The femur is slightly smaller and more slender than 

 the humerus, and is not greatly expanded distally. 



* The name Apractocleidus, meaning idle or functionless'clavicle, has been adopted to accord with the names of 

 the related genera Tricleidus and Cryptocleidus. For the suggestion of the name I am indebted to the Rev. Gavin 

 Waknock, B.D. 



TRANS. ROY. SOC. EDIN., VOL. LI, PART III (NO. 19). 89 



