440 PROF. W. J. SOLLAS ON A NEW SPECIES OF PLESIOSAURUS 



36. On a new Species of Plesiosaurus (P. Conybeari) from the 

 Lower Lias of Charmouth; with Observations on P. mega- 

 cephalus, Stutchbury, and P. brachycephalus, Owen. By W. 

 J. Sollas, M.A., F.B.S.E., F.G.S., &c, Professor of Geology in 

 University College, Bristol. Accompanied by a Supplement on 

 the Geographical Distribution of the Genus Plesiosaurus, by 

 G. F. Whidborne, Esq., M.A., F.G.S. (Bead May 11, 1881.) 



[Plates XXIII. & XXIV.] 



The nearly complete and very fine specimen of Plesiosaurus 

 (PI. XXIII. fig. 1) which forms the subject of the present paper is 

 the latest addition to the already large collection of fossil reptiles 

 preserved in the Bristol Museum. 



It was found over a year ago, by Samuel Clarke of Charmouth, on 

 the north-west corner of Blackven "Water, half a mile west of the 

 river Char, where it lay in a " table-ledge" of the Lower Lias, some 

 seven feet above the " boulder-bed." From its position and the 

 species* of Ammonite still associated with it, we may conclude 

 that its geological horizon is that of the zone of Ammonites obtusus. 



From the pectoral to the pelvic girdle it is imbedded in a layer of 

 hard impure limestone, thick enough to hold the parts securely 

 together, but at the same time thin enough to let the skeleton be 

 seen on both sides, dorsal as well as ventral. The head and neck 

 were preserved chiefly in shale ; so that, to ensure the safety of the 

 neck, it has been found necessary to imbed it in plaster ; but the 

 head, being filled in and about with limestone, has been left free, 

 and can be turned about, handled, and examined on all sides. 



The ventral surface of the fossil (PI. XXIII. fig. 1) is exposed on 

 the upper surface of the imbedding limestone ; the coracoids lie side 

 by side nearly in the position they would have occupied in the dead 

 animal lying on its back, except that they are slightly displaced to- 

 wards the left side ; the left pubis and ischium are also nearly in 

 position ; but the corresponding bones of the right side have been 

 pushed to the left, so as to underlie them ; the femora, which are all 

 that is left of the hind limbs, remain on their proper sides, extended 

 outwards and backwards. The fore limbs have been considerably dis- 

 placed ; for though that of the left remains on its own side, the palmar 

 surface of its hand looking upwards, that of the right has been com- 

 pletely crossed over onto the left, so that its palmar surface would be 

 directly superposed on that of its fellow were it not for a slight dis- 

 location at the distal end of the humerus, which has carried the rest 

 of the right limb backwards, and so left the left hand exposed. The 

 scapulae have turned on their axes, but have not shifted sides ; and 



* This, according to the determination of Mr. Whidborne, is Ammonites 

 planicosta. 



