60 Geological Society. 
cell, and furnishing additional evidence of the existence, in the 
Silurian seas, of forms of Bryozoa which, though very abundant in 
the Oolite and all subsequent periods, were not generally supposed 
to have existed in the Palzeozoic period. 
4, “On a new Species of Plesiosaurus (P. Conybeari) from the 
Lower Lias of Charmouth, with Observations on P. megacephalus, 
Stutchbury, and P. brachycephalus, Owen.” By Prof. W. J. Sollas, 
M.A., F.R.S.E., F.G.8., &¢., Professor of Geology in University 
College, Bristol; accompanied by a Supplement on the Geological 
Distribution of the Genus Plestosaurus, by G. F. Whidborne, Esq., 
M.A., F.G.S. 
The greater part of this paper was devoted to the description of a 
remarkably fine specimen of Plestosaurus from the Ammonites-obtusus 
zone of the Lower Lias, Charmouth. Its distinctive characters are 
as follows :— 
1. The length of the skull is 19°75 in., taken from the anterior 
extremity of the lower jaw to the posterior margin of the quadrate. 
2. There are sixty-six vertebree, of which thirty-eight are cervical, 
twenty-one dorsal, two sacral, and five caudal. 
3. The length of the neck is 83 in.; and the cervico-cephalic 
index is 24-1. 
4, The length of the cervico-dorsal series is 136 inches; and the 
cervico-dorsal-cephalic index is 14-6. 
5. The length of the centrum in the anterior cervical vertebre is 
equal to the height, and greater than the breadth of the articular 
face. In vertebra xv. the measurements are—length 2 inches, 
breadth 1°5 inch, height 2 inches. 
6. In the posterior cervical vertebre the breadth of the articular 
face is greater than the length or height, but the latter two dimen- 
sions remain equal. 
7, The neural spines increase in size up to vertebra xl., in which 
they measure 4-75 inches in length. 
8. The neural spines are inclined backwards as far as vertebra 
ly.; past this, up to lvii., they are inclined forwards; but after- 
wards they again incline backwards. 
9. The humerus and femur are nearly equal in length, the femur 
being slightly the shorter. 
For the species the name of P. Conybeari is proposed. P. Cony- 
bear agrees closely with P. Htheridgi in the relative length of head 
and neck; but it has eight more cervical vertebre than the last- 
mentioned species. _ In the number of the cervical vertebre it agrees 
with P. homalospondylus, but has a much larger cervico-cephalic 
index. 
5. “ On certain Quartzite and Sandstone Fossiliferous Pebbles in 
the Drift in Warwickshire, and their probable Identity with the true 
Lower Silurian Pebbles (with similar fossils) in the Trias at Bud- 
