Page:Quarterly Journal of the Geological Society of London, vol. 26.djvu/843

 3. Note on some Plesiosaurian Remains obtained by J. C. Mansel, Esq., F.G.S., in Kimmeridge Bay, Dorset. By J. W. Hulke, Esq., F.R.S., F.G.S.

(Plate XLI.)

These remains form part of the rich series of Enaliosaurian fossils obtained from Kimmeridge Bay, by J. C. Mansel, Esq., to whose courtesy I am indebted for the opportunity of bringing them under your notice. They consist of five vertebrae, four of which are nearly entire, with pieces of several ribs, a digital phalanx, and a carpal bone (?), imbedded in two slabs of clay-stone, indicating an undescribed species of Plesiosaurus, — and of a large number of associated bones representing another species characterized more particularly by the proportions and peculiar construction of its paddles, which sharply separate it from the typical Plesiosauri of the Lias, and show an extremely close affinity with Pliosaurus.

Plesiosaurus brachistospondylus (Pl. XLI. figs. 7-9).

The middle dorsal vertebrae (the only ones in Mr. Mansel's collection) of the species for which I propose this name, are characterized by the extreme shortness of the centrum, which in three of the vertebrae lying in one slab has a length, or antero-posterior diameter, of 1 inch only, measured along the outer, non-articular surface. The length of the fourth centrum, in the other slab, is .3 inch more ; but this centrum is a little obliquely distorted by pressure. The breadths (or horizontal transverse diameters) of the centra are respectively 4.6, 4.5, 4.3, 4.4 inches ; and their heights (or vertical diameters) are 4, 4, 3.8 inches.

Length. Height. Breadth. Centrum. inch. inches. inches. No. 1 1 4 4.6 No. 2 1 4.5 No. 3 1 4 4.3 No. 4 1.3 3.8 4.4

No. 1. No. 2. Length of transverse process upper border 3.1 2.7 lower border 3.1 2.4

Span between ends of transverse processes 6.7 inches. Height of neural spine about 3.6 inches. Height of entire vertebra from lower border of centrum to top of neural spine about 9.4 inches.

These centra are therefore about four and a half times as broad, and nearly four times as high as they are long — proportions which I have not found in any other Plesiosaurus. The articular faces are gently swollen near the circumference, and hollow at the middle, where the distance between the. two faces in one centrum measures -7 inch. These proportions and the hollow articular faces