MONOGRAPH 
OF 
TPIE FOSSIL liEPTILIA 
OF THE 
LIAS8IC FOKMATIONS. 
Order— SAUROPTERYGIA, Owok 
Gen 118 — Plesiosaurus, Con uheare. 
Species — Plesiosaurus dolicUodeinis, Conybeare. 
(Tabs. I— IV.) 
Of the Plesiosaurus dolicJiodeirus, Conyb., the first described and the typical 
species of the genus, three more or less entire specimens have come under my obser- 
vation, which have been obtained from the Lower Lias of Lyme Regis and Charmouth, 
Dorsetshire. One of these, formerly in the possession of the late Duke of Buckingham 
and now in the British Museum, was the subject of Conybeare’s original description.* 
A second, in the British Museum, is figured by Buckland in his ‘ Bridgewater Treatise,' 
vol. ii, pi. xix, fig. 2 ; the third, also in the British Museum, is the one which I have 
selected for illustration in the present Monograph (Tabs. I and II). In this the 
vertebral series is entire ; there is no break in the long cervical region, as in the other 
two specimens ; its perfection, in this respect, satisfactorily shows that the head is at, 
or nearly at, the correct distance from the trunk, with the neck outstretched, in the 
two former specimens, the greater completeness of which, in regard to the limbs, 
supplies what is wanting in this respect in the present skeleton (see Tab. I, figs. 2 
and 3). 
The condition of the vertebral column in the originally described or type-specimen 
of the Plesiosaurus dolichodeirus is such as to suggest that the carcass, after it sank to 
* ‘Transactions of the Geological Society,’ 2nd series, vol. i, p. 381, pi. xlviii. 
1 
