Vol. 60.] PLESIOSAURUS FROM WESTBURY-ON-SEVERX. 359 



24. On a small Plesiosa tms-SKELETOx from the White Lias of 



WeSTBTJRY-OX-SevERX. By WlXTOUR FREDERICK GwiNNELL, 



Esq., E.G.S. (Read June 8th, 1904.) 



[Abstract.] 



The remains described were found on the Severn beach at Easter 

 1904, and had evidently fallen recently from the cliff above, which 

 is there made up of the Upper Rhaetic Beds, including the Estheria- 

 Bed and the White Lias Limestone. The matrix of the specimen 

 corresponds with the White Lias in colour, texture, and material, 

 and it is similarly traversed by fissures often coated with dendrites. 

 The remains are in excellent preservation, neither pyritized nor 

 appreciably carbonized, as is so usual in ' Bone-Bed ' specimens. 

 They include more than twenty small dorsal vertebrae, with spinous 

 and transverse processes, lying in natural sequence. Pseudomorphs 

 in calcite of the spinal cord and intervertebral cartilages occur also 

 in relative position. Several slender ribs, and indications of other 

 bones (probably from the pectoral or pelvic arches), also occur in the 

 slab, but are not yet worked out. Hitherto only single vertebrae 

 or fragmentary bones of Plesiosaurus have been recorded from the 

 Rhsetics in Britain, and these only from the bone-beds below the 

 White Lias. At present, it has not been found possible to assign 

 the fossil to any existing species, but the characters most nearly 

 approach those of Plesiosaurus bibractensis. 



The specimen has been presented to, and accepted by, the British 

 Museum (Natural History). 



