Miscellaneous. 137 



of a nearly regular, convex, conical form and nearly central tip. The 

 animal of this shell has dissolved a space on the surface of the other 

 Dispotea of the size of the edge of the aperture of its shell. 



No. 5. is a Cardita with a Dispotea on each of its valves placed 

 as in specimen No. 4, that is, with one of the edges of the shell close 

 on the lower edge of the bivalve ; and there is a single valve of the 

 same species of Cardita with another Dispotea in a similar situation. 



It is to be observed, that under each of these shells, instead of the 

 animal having eaten, or rather dissolved away part of the surface of 

 the bivalve so ns to form a smoother surface, each of the animals has 

 deposited on their supporter a circumscribed layer of rather transpa- 

 rent hard calcareous matter of the exact size and form of the mouth 

 of the shell, which fills up the greater part of the space between the 

 ribs and forms an even and smooth base, and in one case it covers over 

 some Serpulte and other bodies which were attached to the bivalve. 

 I cannot find any indication of a muscular scar on this deposit. 

 These Dispotece have a thick pale brown shell, darker towards the 

 upper part of the cavity ; the outer surface is covered with thick, ir- 

 regular, radiating, flattish- topped ribs, crossed by irregular concentric 

 ridges, having oblong or linear intervening nets, and the surface of 

 one of the specimens is marked with some irregular cross-ridges 

 caused by the inequalities of the shell. In one of the Dispotea the 

 internal appendage or back of the shell is near the lower edge of the 

 bivalve, and the other has it near the umbo. 



I believe that the whole of these specimens belong to a single 

 species (No. 1 to 4 is D. tubifera. Say, and No. 5 is D. rugosa. Les- 

 son), but it is curious to observe, that when within the cavity of an- 

 other shell, it is white, low, and the animal did not dissolve any part 

 of the surface to which it was attached ; that when on the out«r 

 surface of the shell, it is high, thick, dark brown, and in some cases 

 it a'osorbs the surface to which it is attached ; and at others that it 

 deposits a layer on the surface of the shell to which it is afi5xed, of 

 the size of the margin of the shell itself. I may observe that generic 

 characters have been formed on less variations in habit and less 

 characters. 



In the same collection are two specimens oiPecten with two Crepi^ 

 dula on each : they have modified the form of the surface of each shell, 

 and the animals have absorbed a very thin layer from the surface of 

 each part of the shell to which they are attached. — J. E. Gray. /■ 



On the Embryology of Actseon. By M. Vogt*, ____, 



The embryology of the Actaon has been the principal object of J 

 my researches ; I have seen the coupling of this interesting little 

 moUusk, I have been present at the laying of the eggs, which takes 

 place during some hours after the coitus, and I have thus had an 

 opportunity of following, from hour to hour, up to the present day, 

 the changes which the egg undergoes during a month. I have thus 

 been able to ascertain that the separation of the vitellus is complete 

 in this species, and that the division into eight parts offers a very 



* Extract of a letter addressed to M. Milne Edwards. 

 Ann^^ Mag, N, Hist, VoLw'iu L 



