110 
ICHTHYOSAUR1A FROM THE 
ICHTHY OSAURIA 
FROM THE OXFORD CLAY OF PETERBOROUGH. 
Exhibited in Cabinets I. and II. 
The fossils in Case I. and shelves a and b, Case II. are 
the bones of one Ichthyosaurus from Woodstone Lodge near 
Peterborough, and a portion of the Collection formed by the 
late Dr Henry Porter. They comprise on Case I. a and 
I. b separate bones of the head, and on the remaining shelves 
of Case I. vertebrae, of which the atlas and axis were anchy- 
losed; there was an inferior w T edge-bone, which was not 
anchylosed. These are followed by 24 other cervical verte¬ 
brae, in which the centrum gradually enlarges in passing back¬ 
ward, and in which the upper head for the rib was entirely 
supported on the neural arch in all except the last. With 
this character in all known animals is associated a four-celled 
heart. The neck vertebrae are about twice the usual number. 
Twenty-three vertebrae, progressively enlarging, have gradu¬ 
ally descending down the side of the centrum the double 
tubercle for the double-headed rib. Then come 32 caudal 
vertebrae, decreasing in size, with a single tubercle for the 
rib, at the base of the side of the centrum, and these are 
succeeded by 14 terminal caudal vertebrae, which do not sup¬ 
port ribs, and continue to diminish in size. 
