482 Miscellaneous. 



locality, which I have received from Mr. Hon aid Gunn, proves most 

 decidedly, what I had long suspected, that they are very different 

 species, and they may be characterized as follows : 



Trigonia margaritacea, Lam. Syst. Anim. sans Verteb. — Shell ra- 

 ther compressed, with 20 or 23 rather narrow nodulose radiating 

 ribs ; the hinder ribs very compressed, all excepting the front ribs 

 wide apart. Hab. Van Diemen's Land. Honald Gunn, Esq. 



Trigonia Lamarckii, Gray. — Shell rather ventricose, solid, with 20 

 to 26 narrow flat-topped nodulose radiating ribs ; the ribs of the 

 hinder slope, narrow, rather crowded ; convex, ribs all close together 

 and nodulose. Hab. New Holland, Port Jackson. Mr. Stutchbury. 



Varies with the inside white, salmon-coloured, yellow, or purple 

 bronze. 



The young states of these two species are so very different that it 

 is astonishing they could have ever been confounded ; the Van Die- 

 men's Land species in all its stages of growth is about twice as large 

 as that from New Holland. — J. E. Gray. 



THE SEXES OF LIMPETS. PATELLAE. 



The Patella have generally been considered as hermaphrodite, but 

 this is certainly not the case, as I have remarked several years ago. 

 But notwithstanding repeated examinations, however, I have not 

 been able to discover any external difference in the animal, except a 

 slight variation in colour, nor is there any difference in the size and 

 form of the shells. In the autumn they are easily distinguished if 

 an incision be made along the right side of the foot, when the males 

 exhibit a white milky glairy fluid ; and the females, which before 

 they are cut generally have a darker foot, a great quantity of round 

 eggs (the size and appearance differing according to their state 

 of development) swimming in a transparent viscid fluid. This can- 

 not be the two states of the same fluid, for after examining hun- 

 dreds of specimens, of different sizes and at various seasons, I have 

 neverbeen able to find them in any intermediate state, although I have 

 found the egg in various stages of development. In their early state 

 they are dark and opake, but in the later they become more transpa- 

 rent. I have never been so fortunate as to find the foetal state of the 

 animal, showing the primitive form of the shell ; but this state may 

 often be seen attached to the tip of the young specimens. 



The larger limpets often form on the chalk, cavities the size of 

 their shell, as I have noticed in my paper on the structure of shells, 

 in the Philosophical Transactions for 1833. — J. E. Gray, 



