PLESIOSATJKIDJE. 267 



neural spines comparatively short, with squared summits. Pectoral 

 girdle not exposed. Humerus much shorter than femur. Radius 

 and ulna and tibia and fibula relatively very short; 8 bones in 

 carpus and tarsus. 



P. braehycepJiaJus was distinguished solely on account of the 

 lower position of the costal facets of the later cervical vertebrae — a 

 character which may apparently well be due to maturity, the type 

 being in all other respects identical with the immature type of the 

 present species. 



Hob. Europe (England). 



R. 1336. Slab exhibiting the dorsal aspect of the skull and paddles 

 (Fig.) and the right lateral aspect of the vertebral column of a 

 half-grown individual ; from the Lower Lias of Lyme- 

 Regis, Dorsetshire. The type specimen. Described by 

 Owen in the ' Rep. Brit. Assoc' for 1839, p. 62, and 

 described and figured by the same writer in the ' Trans. 

 Geol. Soc' ser. 2, vol. v. pp. 515-535, pis. xliii.-xlv. 

 Also figured by Buckland in his ' Geology and Mine- 

 ralogy ' (Bridgewater Treatise), pi. xix. fig. 1, and by 

 Haughton in his 'Manual of Geology,' fig. 39, facing 

 p. 27-1. The head and neck are twisted round to the 

 left ; the greater part of the caudal region and the right 

 pelvic limb are wanting. In the cervical region the ribs 

 are displaced, permitting the junction of the costal with 

 the neurapophysial facets to be beautifully shown. The 

 eight carpal bones are shown in both limbs, but only six 

 tarsals remain in the pelvic limb. AVith the exception 

 of the left scapula, only the borders of the pectoral 

 and pelvic girdles are visible. The length of the cranium 

 is about 0,215 (8-5 inches), and that of the mandible 

 0,2G9 (10-5 inches). The humerus has a length of 

 0,101 (4-0 inches), and the femur of 0,120 (4*7 inches). 

 The resemblance of this specimen to the larger type 

 skeleton of P. brachycephalus figured by Sollas in the 

 * Quart. Journ. Geol. Soc' vol. xxxvii. pi. xxiv. fig. 2, is 

 so close as to render it almost certain that the one is the 

 immature condition of the other. The adult skeleton 

 indicates an individual somewhat less than twice the size 

 of the present specimen, the length of the skull being 

 0,354 (14 inches), that of the humerus 0,227 (9*0 inches), 

 and that of the femur 0,247 (9-7 inches). 



Purchased from the Karl of Ennislcillen. 



