376 TEE PORTLAND OOLITE PERIOD. CHAP. 



haemal spines are confined to the posterior edge. The neural spine 

 can only have been small. 



The length being o'8 inch, the breadth of the articular face is 

 1-8 5 the height to the canal, 1-25 ; concavity, 0-2. From point to 

 point of the lateral processes, which are firmly anchylosed, is 3-25. 



MACROSPONDYLIAN PLESIOSAURI. 



A group of plesiosauri, characterized by having vertebrae of 

 greater than the usual length in proportion to breadth, and more 

 or less cylindrical bodies, plane or very slightly concave on the 

 faces, is represented by specimens from Shotover, Garsington, Hat- 

 ford, Abingdon, and Brill. There are probably two or three species, 

 but not sufficient specimens to furnish good characteristics. 



The largest cervical vertebra from Garsington is 3-90 inches long, 

 and about 3*20 in diameter : or, length, 100 ; diameter, 82. 



The dorsal vertebrae are shorter in proportion on an average : 

 length, 100 ; breadth, 108. 



PECTORAL AND PELVIC GIEDLES OF PLESIOSAUEIANS. 



The diagrams whicb follow may be useful as shewing the 

 principal forms of the coracoidian and pelvic bones, which appear 

 to belong to the genus plesiosaurus, but cannot with confidence 

 be referred to the respective species already indicated by vertebrae. 



Fragments of a pair of ischial bones from Shotover, in general 

 form resembling those of Plesiosaurus Oxoniensis (Diagram CXVL), 

 were obtained from Shotover previous to 1854, and have been now 

 adjusted. The bones had been subjected to oblique crushing, so 

 as to injure the symmetry more than the drawing represents. The 

 symphysial line is somewhat cariniform, and is straight for a 

 considerable length. The sharp ridges which pass from the outer 

 parts of the articulating ends begin to subside at a distance of 

 twelve inches in their course toward the margins, from which to 

 their origin is 21 inches ; the breadth over the condyles being 22*5. 

 The condyles are formed on two slopes inclined to one another 108, 



