PROCEEDINGS 
OF 
THE GEOLOGICAL SOCIETY OF LONDON. 
Voz. III. 1839—1840. No. 66. 
December 4.—Angus Friend Mackintosh, Esq., Chenies Street, 
Bedford Square, was elected a Fellow of this Society. 
A paper was first read, entitled «‘ A Description of the Soft Parts 
and of the shape of the Hind Fin of the Ichthyosaurus, as when re- 
cent,” by Richard Owen, Esq., F.R.S., F.G.S. 
The osseous frame-work of the fin of the Ichthyosaurus, Mr. Owen 
observes, having alone been the subject of direct examination, the 
exact shape and the nature of the soft parts had been matters of 
conjecture. A very striking deviation from the reptilian and mam- 
malian types had, indeed, been recognised, and resemblance also to 
the fins of fishes had been admitted in the digits of the fin exceeding 
five, in their being sometimes bifurcated, and in consisting of an ex- 
traordinary number of ossicles; yet owing to the form of the digital 
ossicles, their breadth and flatness, and their large size, as compared 
with the joints of the fin-rays of fishes, it had been generally sup- 
posed that the locomotive organs of the Ichthyosaurus were en- 
veloped, while living, in a smooth integument, which like that of 
the turtle and porpoise, had no other support than was afforded by 
the bones and ligaments within. 
Sir Philip Grey Egerton ina recent examination of Ichthyosaurian 
remains in the possession of Mr. Lee of Barrow-on-Soar, detected, 
with the penetration which has enabled him to bring to light many 
other obscure points in the structure of the Ichthyosaurus, traces of 
the soft parts of the fin in a slab of lias containing a mutilated pad- 
dle; and having submitted the specimen to the examination of Mr. 
Owen, a detailed account of its character forms the subject of this 
memoir. 
Mr. Owen considers the specimen to be a posterior fin of the 
Ichthyosaurus communis. It presents impressions and fractured por- 
tions of six digits, with the impression,—and a thin layer, most di- 
stinetly preserved,—of the dark carbonized integument of the ter- 
minal half of the fin, the contour of which is thus most beautifully 
defined. 
The anterior margin is formed by a smooth unbroken well-marked 
line, apparently a duplication of the integument; but the whole of 
the posterior margin exhibits the remains and impressions of a series 
of rays by which the fold of the integument was supported. Imme- 
diately posterior to the digital ossicles, is a band of carbonaceous 
matter of a distinctly fibrous structure, varying from two to four 
VOL, III, fo) 
