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XIX. — A Description of some of the Soft Parts, ivith the Integument, of the 

 Hind-fin of the Ichthyosaurus, indicating the Shape of the Fin when 

 recent. 



By RICHARD OWEN, Esq., F.R.S., F.G.S., etc. 



[Read December 4, 1839.] 

 Plate XX. 



JilTHERTO the exact shape and the nature of the soft parts of the paddles of 

 the Ichthyosaurus have been matters of conjecture ; the bony framework of these 

 locomotive organs has alone been the subject of direct observation. But this part 

 of the skeleton presents a striking deviation from the Reptilian and Mammalian 

 types, inasmuch as in all existing air-breathing Vertebrates the number of digits of 

 a locomotive member never exceeds five ; while in the fore-fins of the Ichthyosaurus 

 communis they are at least seven, of which some are bifurcated, and all consist of 

 an extraordinary number of phalanges*. And, therefore, notwithstanding that the 

 shape of these digital ossicles, their breadth and flatness and their large size, as 

 compared with the joints of the fin-rays of Fishes, clearly indicate that the paddles 

 of the Ichthyosaurus were enveloped in a smooth integument, the inference that the 

 integument, as in the paddles of the Turtle and Porpoise, had no other support 

 than was afforded by the bones and ligaments within, is less conclusive ; and any 

 direct evidence of the nature of the more perishable parts of the fin of the Ichthy- 

 osaur becomes pecuharly acceptable, when we attach due weight to the approxi- 

 mation to the Ichthyic structure made by the more enduring parts. 



Sir Philip Grey Egerton, while examining a collection of Ichthyosaurian remains 

 in the possession of Mr. Lee, of Barrow-on-Soar, with the same happy penetration 

 which has already brought to light some of the most obscure and interesting points 

 in the structure of the vertebral column of the Ichthyosaurus, detected the traces 



* There are upwards of two hundred phalangeal ossicles, besides the eight metacarpals, in the fore-fiu 

 of the Ichthyosaurus communis. 



