Sir P. dc jMalpas Grey Egerton on Chondrosteus. 61 



body, and ha^"ing communication with the surface only through the 

 medium of canals, which are sometimes continued into short bristles, 

 and sometimes terminate in mere bulbs. As a prehensile organ, the 

 claw needs sensibility, but no force which the animal could exercise 

 could make any impression on the parts within, through its dense 

 tuberculated edges. On the other hand, it is difficult to assign any 

 office to the bristles, and still more to the bulbs, mechanical or 

 otherwise, unless it be that which has been suggested, — that, cstablish- 

 ine, as they do, a communication between the external surface and the 

 nervous structure within, they communicate impressions, and are in 

 fact tactile organs. 



The author had satisfied himself, before the appearance of Dr. 

 Hackel's paper, that the hairs were connected with the inner layers 

 of the corium, and not with the chitinogenous membrane only ; and he 

 had seen indications in the lobster and larger Crustacea of an arrange- 

 ment of the pulp corresponding to the arrangement of the hairs. 

 In the smaller Crustacea, especially in the shrimps, he found a re- 

 markable confirmation of his views. In the flabelliform processes, 

 and even in the claws in these animals, he found that the structures 

 within the shell were arranged in the form of tubes corresponding to 

 the hairs, through which passed from the deeper parts, fibres which 

 were prolonged into the hair-canals. In the claw the nerve was 

 traced to the inner termination of these tubes. The tubes in some 

 instances merged internally into the general mass of the corium; in 

 others they were truncated. Externally, or towards the margins, they 

 presented open orifices, through which the fibres passed. The fibres, 

 when drav\-n out from the hair-canals, often presented the plumose or 

 serrated character, according to the form of hair to which they 

 belonged. They could be traced for some distance down the tubes, 

 and at times completely through them, but their deep connexions 

 could not be clearly made out. Several modifications of this arrange- 

 ment are described and figured. The author believes that the facts 

 brought forward are sufficient to establish that the hairs of the Crus- 

 tacea are probably organs by which external impressions are com- 

 municated to the internal sensitive parts. 



May 6, 1858. — The Lord Wrottesley, President, in the Chair. 



" On Chondrosteus, an extinct genus of Fish allied to the Sturio- 

 nidae." By Sir Philip de Malpas Grey Egerton, Bart., F.R.S. 



Before the conclusion of his great work on Fossil Fishes, Pro- 

 fessor Agassiz recognized in some fragmentary remains found in the 

 lias strata at Lyme Regis, uumistakeable evidence of the existence, at 

 that period of the earth's deposition, of a representative of the still 

 extant family of the Sturgeons. To this extinct fish he assigned 

 the name Chondrosteus. The author of the present memoir has 

 been enabled, by the examination of numerous specimens more re- 

 cently acquired, to describe in some detail the external features of 

 the fish, and the structural peculiarities of those portions of the 

 exo- and endo-skeleton which have Ijeeu preserved. In the former 



