344 Structure of the Fossil Saurians. 



paddle is, with the humerus, 1\ in. long, and 3 in. broad ; 

 the hind paddle, in length and breadth, somewhat less. 



c, Ichtiiyosau'rus platy^odon Dc la Bcche cl Conyb. 



According to Conybeare, this species is the most colossal, 

 and to it belong the gigantic individuals. The crown of 

 the teeth is flattened, and possesses on each side a cutting 

 edge. These crowns are borne on a round and expanded 

 shank or root. Dr. Davis has found in the neighbourhood 

 of Bath a vertebra of this species, which measures 7 in. in 

 diameter. There are jaws 8 ft. long. 



d. Ichthyosau'kus interme^dius De la Bcche cl Conyb. 

 The teeth are more pointed, and less deeply striated, than 

 in the I. communis, and less long than in the I. tenuirostris. 

 This species does not attain half the size to which I. platyo- 

 don may arrive. 



e. Ichtiiyosau'rus Conybeare. 

 Conybeare observes that the cervical vertebrae of the Ichthy- 

 osaurus from the Kimmeridge clay differ from those already 

 mentioned, and therefore belong to another species. 



/. Ichthyosau'rus Cuvicr. 

 Cuvier mentions a ridge-shaped bone, which is very thick, 

 and formed almost like a half moon, and whose two canals 

 unite behind in a single transverse opening. He therefore 

 conceives it to have belonged to none of the first four spe- 

 cies. 



g. Ichtiiyosau'rus Harlan. 

 Harlan describes remains which differ from those of the 

 four Ichthyosauri established by Conybeare, in the greater 

 relative thickness of the dental bones : this species most 

 nearly approached the I. communis. The largest teeth are 

 two thirds of an inch long, and elevated about three tenths 

 above the jaw; the protruding part is thickly striated length- 

 wise ; and in the concealed portion of the tooth are farther 

 observed longitudinal lines. The tooth, from the basis to the 

 point, is of a conical shape.* 



h. Ichthyosau'rus gra'ndipes Sharpe. 



On the 16th of April, 1830, Sharpe read to the Geological 

 Society of London the description of a new species, which 

 was found in the lias, 4 miles from Stratford upon Avon. 



* Harlan calls this species I. eoniformis. The fragment from which he 

 described it came from Bristol. May it not be the Thecodontosaurus of 

 Dr. Riley and Mr. Stutchbury ? — Ed, 



