Mr. H. Seeley on Plesiosaurus macropterus. 49 



about \\ millim. In the middle of the body, its lower half is 

 fully one-third deeper than the upper half. The colourless body 

 exhibits along the dorsal ridge, as also on each side near the 

 intestine, a series of black points, and beneath the chorda five 

 oblique lines of the same colour, corresponding to the com- 

 mencement of the ventral portions of the muscles. 



Total length, 0*088 metre ; head, 0-0035 ; from the tip of the 

 muzzle to the posterior margin of the eye, 0002 ; from the anus 

 to the extremity of the tail (without the fin), 00033; depth of 

 the middle of the body, 0*013. 



Younger specimens, 0'060 metre in length and 0007 [in 

 depth] present precisely the same structure and proportions, 

 which would furnish a sufficient proof, if such were wanted, that 

 the Leptocephali are not mere larval forms of Cepola or other 

 Ribbon-fishes. We have had the opportunity of seeing quite 

 young specimens of Cepola and other Ribbon-fishes, and have 

 always been able to recognize their genus, notwithstanding the 

 well-known peculiarities of the young state. 



Dr. F. Jagor, to whom we are indebted for this beautiful 

 species, took eight specimens of it, of various sizes, in the open 

 sea between May bate and Luzon. 



IX. — On Plesiosaurus macropterus, a new Species from the Lias 

 of Whitby. By Harry Seeley, F.G.S., Woodwardian Mu- 

 seum, Cambridge. 



One of the ornaments of the Woodwardian Museum is a grand 

 Plesiosaur, beautifully displaying the general relations of the 

 bones. It was obtained in L842 by the energy of the venerable 

 Professor of Anatomy, who, being on the spot when it was found, 

 secured it for the University, when it was purchased by subscrip- 

 tion, and confided to the care of the Woodwardian Professor. 



The reptile rests nearly flat on the ventral side, in a natural 

 extended posture, the tail only being two or three times bent. 

 But the same hard concretionary limestone which preserves the 

 relations of the bones so well, invests much of the vertebral 

 bodies, so that their relative proportions in form and size are 

 partly obscured. 



Hitherto there have been but six species of Plesiosaurus de- 

 scribed from entire specimens ; and with those chiefly our new 

 one will be compared in this brief notice. 



The chief characters of the several species, as stated by Pro- 

 fessors Owen and Huxley, Mr. Baily and Dr. Carte, are the 

 following : — 



Ann. ty Mag. N. Hist. Ser. 3. Vol. xv. 4 



