PLEUROSTERNLDJi;. 209 



has a pedunculate glenoid cavity, as in Hydrastis, where, 

 however, the scapula and precoracoid form an acute, in- 

 stead of a right angle at their junction. 



Purchased^ 1865. 



40676. Slab showing the dorsal aspect of the imperfect carapace ; 

 from the Purheck of Swanage. The middle line is some- 

 what damaged. Purchased, 1867. 



40960. Slab exhibiting the dorsal surface of the imperfect posterior 

 portion of the carapace, and the ventral surface of the 

 associated plastron : from the Purbeck of Swanage. The 

 xiphiplastrals are wanting ; the entoplastral exhibits the 

 characteristic breadth. Purchased, 1868. 



R. 911. The plastron, imperfect posteriorly ; from the Purbeck 

 (Fig.) of Swanage. The type specimen ; figured by Owen in his 

 4 Reptilia of the London Clay, &c.' (Mon. Pal. Soc), vol. i. 

 pt. i. pi. xxi., where it is incorrectly stated to have been 

 obtained from the London Clay. It is also described by 

 the same writer in the ' Eep. Brit. Assoc/ for 1841, 

 p. 164 ; and is noticed by Eiitimeyer in the « N. Denkschr. 

 schw. Ges. Nat.' vol. xxv. art. 2, pp. 159-160, who first 

 pointed out its close resemblance to the plastron of No. 

 46317, and stated that it must clearly be referred to the 

 genus Pleurosternum. The specimen is again noticed by 

 G. A. Boulenger and the present writer in the ' Geol. Mag.' 

 dec. iii. vol. iv. p. 271 (1887), where its true geological 

 horizon is mentioned. 



Purchased at the sale of Bullock's Museum. 



46832. The plastron, imperfect posteriorly; from Swanage. The 

 specimen is broken off" across the hypoplastral, the fracture 

 on the right side extending into the mesoplastral. On the 

 inner aspect there is preserved the crushed pectoral girdle 

 of the left side, together with the proximal half of the 

 humerus. The expanded contour of the coracoid can 

 still be clearly seen. Purchased, 1875. 



R. 1524. Slab containing the imperfect plastron ; from Swanage. 



(Fig..) The left hyoplastral is detached and seen from the ventral 

 aspect. The meso- and hypoplastrals are also exhibited 

 chiefly from the ventral aspect ; but the distal portion 

 of the hypoplastrals and the xiphiplastrals has been 

 cleared from matrix in order to exhibit the articular facets 



PART III. . p 



