LIASSIC PLESIOSAURS. 177 



especially in tlie third, fourth, and fifth of the series. The anterior marginal now 

 presents, indeed, the characters of a normal digit, and by its articulation with the 

 radio-carpal ossicle seems to displace the foremost or true radial from its carpal or 

 metacarpal connection. At the ulnar border of the modified paddle are two series 

 of the small rounded marginal ossicles; nevertheless the number of phalangeal 

 and marginal ossicles is such that the chief characteristic of this paddle is its 

 superior length in proportion to its breadth. . 



SUPPLEMENT TO CHAPTER l.—Sauropterygia. 



Flesiosaurus macrocephalus, Owen. Enaliosauria, PI. 17. 



For the unique specimen figured in the above plate the British Museum is 

 indebted to the Earl of Enniskillen, who, when Lord Cole, obtained it during 

 one of His Lordship's visits to Lyme Regis in quest of the fossils from the Liassic 

 deposits in that locality ; and I was favoured by its transmission for determination 

 and description. It was in a rare condition of preservation, as may be conceived 

 by the Plate, and obviously differed from the species, at that date (1838), 

 described and figured by Conybeare and Hawkins. 



The first distinction which arrested attention was the greater relative size of 

 the skull. (Compare PI. 17 with PL 1, Plesiosauriis doticJwdeirus and PI. V, 

 Flesiosaurus homalospo^idylus.) In correlation with the weightier head is a rela- 

 tively stronger and shorter neck, though this retains sufficient of the characteristic 

 proportion of the part in the present singular extinct Order of marine Reptilia : 

 it is twice the length of the lower jaw, and includes twenty-nine vertebrge. 

 Diff"erential characters are also shown in the jjroportions of individual vertebrse ; 

 in the twentieth, counting from the skull, the transverse is to the fore-and-aft 

 diameter as 2 to 1 ; in a corresponding vertebra of Flesiosaurus Haivldnsii it is as 

 4 to 3. The short cervical ribs, which, as usual in the Order, are mostly hatchet- 

 shaped, resume the more normal syliform character at the twenty-fifth vertebra ; 

 in Flesiosaurus Jiomalospondylus. This change does not take place until the 

 twenty-ninth vertebra, the number of cervicals being thirty-one ; in Fles. 

 macrocephalus it is twenty-nine. I still adhere to the character defining the 

 cervicals in the present long-necked Reptiles, viz. holding that vertebra in which 

 the costal articular surface has risen from the centrum to the neurapophysis, as 

 the first or foremost of the dorsal series. As many successive vertebrse as 

 show the rib-bearing processes on the neural arch I reckon as " dorsals." 

 Of these there are twenty in Fles. macroceplialus, and twenty-three in Fles. 

 23 



