20 BRITISH FOSSIL REPTILES. 



there, in proportion to its length, than in the PI. dolichodeirus or than in the 

 PL rostratiis ; its anterior margin, as in the skeleton Tab. V, is more straight than in 

 those species. The antibrachial bones (54, 55) show intermediate proportions of 

 length and breadth between those in PI. dolichodeirus (Tab. I, fig. 2) and PI. roHtratus 

 (Tab. IX). They present the usual characteristics of radius (54) and ulna (55) in the 

 present genus, and they are of equal length. The hand measures two feet in 

 length, and is somewhat longer in proportion to the arm and forearm than in the 

 two above-cited species ; it also shows rather more breadth. The carpus consists of 

 six bones, three in each row, and with less inequality of size. The distal bones 

 occupy an equal breadth with those of the proximal row, and do not allow the base 

 of the fifth metacarpal to extend backward to the proximal row, as in the species 

 of which the carpus is figured in Tab. XIV. The bases of the five metacarpals 

 (in Tab. VIII, 57) are on the same transverse line ; and if this specimen should truly 

 exhibit the relative position of the bones of the pectoral fin, characteristic of the 

 species, it adds a well-marked distinction of the PI. homalospondylus. The first, or 

 radial, or innermost metacarpal (57), supports a short digit of three phalanges ; the 

 second a digit of seven phalanges ; the third the same ; the fourth has a digit of six 

 phalanges ; the fifth is obviously imperfect. 



The pelvic limb (Tab. VIII, G5, 69) is 3 feet 9 inches in length ; the femur (65) is 

 14 inches long and 7^ inches across the distal end. The tibia and fibula are respec- 

 tively longer than their homotypes the radius and ulna ; the foot is 2 feet in length 

 and 1\ inches in basal breadth. The tarsal bones are similar in number and arrange- 

 ment to those of the carpus ; and as the bases of the five metatarsals (69) are in this 

 limb also on the same transverse line, I have the greater confidence in the natural 

 structure being here shown in both limbs, and that they thus exhibit a distinctive 

 character, of specific value, from the other Plesiosauri described in the present 

 Monograph. 



Plesiosaurus rostratus, Owen. Tabs. IX — XIII. 



The specimen on which this species is founded was obtained, in 1863, by Edward 

 C. Hartsinck Day, Esq., F.G.S., from the Lower Lias at Charmouth, Dorsetshire, by 

 whom it was transmitted to London for inspection, and it has been purchased 

 by the Trustees of the British Museum, where it is now exposed in the gallery of 

 Geology. It is figured, one ninth of the natural size, in Tab. IX. 



This skeleton, like most of the plesiosaurian ones that have come under my obser- 

 vation, indicates the ordinary and tranquil character of the death and burial of the 

 individual ; it has sunk entire, relaxed, and prone, with outstretched limbs, in its 

 matrix, when this was soft and yielding ; and, as decomposition loosened the liga- 



