154 REI^TILES. SAURIA. 



1825, for the reception of the bones of an animal found in the 

 ironsand of Tilgate Forest, near Cuckfield, in Sussex. This 

 reptile appears to have been herbivorous, and to possess a close 

 affinity with the recent Iguana of the West Indies. Mr Man- 

 till considers the animal as having been upwards of 60 feet in 

 length.— Annals of Philosophy, March 1825, p. 223. 



ENALIO SAURI. 



In this group of Saurian Reptiles, instituted in a paper by H. T. 

 de la Beche and the Rev. W. D. Conybeare, Geol. Trans, v. 559, 

 the extremities are four in number, terminating in paddles, composed 

 of a series of flat polygonal bones, constituting organs fit for swim- 

 ming, but incapable of executing progressive motion on the land. 

 The eyes are large, and the sclerotica is strengthened by a circle of 

 osseous pieces ; — a character which establishes an affinity with birds, 

 lizards and tortoises, to the exclusion of crocodiles and fishes. 



IV. Ichthyosaurus. — Tliis genus, the characters of which have 

 from time to time been developed by Sir E. Home, in the Phi- 

 losophical Transactions of the Royal Society of London from 

 1814 to 1820 inclusive, and more recently by Mr Conybeare, 

 exhibits the snout of a dolphin, the teeth of a crocodile, the 

 head and sternum of a lizard, and the swimmers of a whale, 

 with the vertebrae of a fish. The extremities have no distinct 

 radius and ulna ; but the humerus supports immediately a nu- 

 merous series of polygonal bones. The anterior extremities are 

 the largest. Dentition like the crocodile, the young tooth grow- 

 ing up in the interior of the cavity of the old one, and, when 

 matured, splitting, and causing it to fall. Teeth numerous. 

 Vertebrae from 80 to 90. The following species have been es- 

 tablished. 



1. I. communis Teeth with conical summits, moderately pointed, slight- 

 ly bent and deeply striated. This is the largest of the species, and occurs in 

 the Lias. It is "probably the one figured by Mr Young, Wern. Mem. iii. 

 p. 450. tab. xxii. 



2. I. Plaiyodmi. — Teeth witli compressed summits, with a sharp ridge on 

 each side. 



3. I. tenuirostris Teeth slender ; nose produced — Home, Phil. Trans. 



1819, tab. XV. 



4. I. intermedins. — Teeth more pomted, and less deeply striated, than in 1. 

 communis. 



These different species are distributed in the strata of the lias and oolitic 

 formations. Dr Harlan has proposed to add another species to the British 

 list, which he supposes to have come from the neighbourhood of Bath or Bris- 

 tol. It resembles the I. communis; but he says that the teeth are more 

 aduncate, and the dental bone of greater relative thickness. He proposes to 

 term it I. cmiiformis Journ. Acad. Phil, iii. p. 336. tab. xii. f. 6, 7, 8. 



V. Plksio^aurus. — This genus was instituted by Mr Cony- 



beare. With the swim.mcrs of a whale, and the head of a lizard. 



