86 



SHELLS AND SHELL-FISH. 



each presents a graduated link between the thin and 

 brittle Ficula papyracea and the strength and solidity of 

 the other types. The whole of the FiculcB are smooth, 

 except one species*, which has some very slight tubercles; 

 but in Rapella, these tubercles, where they exist, begin 

 to put on that foliated structure so prevalent in the next 

 genus ; and in others there are indications of longitu- 

 dinal plaits upon the body whorl : the outer lip, how- 

 ever, is still very thin, and the whole may be described 

 as a group of generally smooth shells : in one or two 

 species, the inner lip is so much developed at its base, as 

 actually to fill up and cover the umbilicus. Yet, in all 

 the variations we have enumerated, the chief generic 

 characters are constant, and the basal canal is always 

 small. 



(74.) We now come to the fourth type, or the genus 

 Myristica, — a name we exalt from a specific to a generic 

 signification for the shell now known as the Pyr-ula my- 

 ristica, and which we shall here call Myristica coronata. 

 These are the most dissimilar from the typical groups 

 we have yet noticed : the form indeed, somewhat pear- 

 shaped, — inasmuch as the spire is not longer than the 

 contracted part of the aperture, from which the canal 

 may be said to commence ; but they have nothing of 

 the lightness or the basal elongation of Pyrula and 

 Ficula, or of the effuse aperture and contracted chan- 

 nel of Rapella. They may thus be described as very 

 short, strong, fusiform shells ; the umbilicus either 

 entirely or partially concealed ; the outer surface armed 

 with muricated and semi-foliaceous spines, and marked 

 with transverse striae ; the inner lip vitreous, but thin ; 

 the outer lip with an ascending channel above, and a 

 wide and distinct one at the base. Now, between this 

 and the last group there is a series of connecting links 

 which unite them in the most perfect manner to each 

 other ; few of them, however, are figured in the more 

 general conchological works. We may here remark, 

 that the P. hippocastanum and lineata t of Lamarck are 



* See Sowerby's Genera. f Ency. Meth. pi. 432. fig. 4, 5. , 



