DKECIOUS MOLLUSCA. 357 



sort of their money : they grow on the bottom of sea-bays, 

 and the shels are like Periwinkles, but greater. Whilst they 

 are very small, and first growing, many of them are within 



Fig. 72. 



9 1? 



one of the concave receptacles of these matrices, which are 

 very tough, and strong, so contrived, that they are separate 

 from one another, yet so, that each of them is fastened to 

 a kind of skin, subtended all along to all these cases or 

 baggs."* Ellis has figured and described the same, or a 

 very nearly allied one, with his usual accuracy : " The 

 ovaries, or matrices, are of a compressed oval form, and 

 some of them of the shape of the Limpet or Patella, but 

 flatter at the top. These are united on one side to a tough 

 pliable ligament, so near to each other as to seem to lie on 

 one another. On the front edge, opposite to where they 

 are fastened, is the arched door, by which the young ones, 

 when they are capable of providing for themselves, make 

 their retreat into the sea. The valve that covers this door 

 during their minute state, is a most curious contrivance to 

 preserve the tender animals from the sea-water till they are 

 able to venture into it. During their confinement, they are 

 covered with a slime like the white of an egg ; which, no 

 doubt, nourishes and promotes the growth of the young 

 animals. If we attentively consider this string of ovaries, 

 we shall be apt to conclude that both they, as well as the 

 animals, grew after they were deposited by the parent 

 Whelk ; for they appear by much too large for even the 

 largest of this tribe ever to have contained. At first sight, 

 they have the appearance of something belonging to the 

 vegetable tribe, and are not unlike the strings of seed-vessels 

 of the Hop hornbeam. "-j~ 



* Phil. Trans. 1670, p. 1152 ; also vol. xvii. p. 871. 

 t Corallines, 85, pi. 33. fig. a, A. Phil. Trans, abridg. iii. 573. The 

 nidus is that of the Murex canaliculatus, Linn.=Pymla canaliculata, Brug. 



