97 



CHAP. IV. 



THE ZOOPHAGA, OR PREUACEOUS SHELL-FISH, CONTINUED. THE 

 FAMILY OF VOLUTID^E, OR VOLUTES. 



(85.) WE now come to one of the most interesting 

 and beautiful families of the spiral Testacea; whether in 

 regard to the elegance of the shells themselves^ or as 

 exhibiting a principle of variation in their structure 

 which can hardly be excelled. Our knowledge of the 

 animals themselves has been much increased, of late 

 years, by the French naturalists, and by the exquisite 

 drawings of Guilding. To generalise these discoveries, 

 however, so as to assign some undeviating character to 

 the whole, is almost impossible. The only peculiarity 

 appears to be the absence of any operculum : in the ma- 

 jority, the eyes are sessile, placed at the base of two 

 short tentacula, and as much developed, in the typical 

 volutes, as they are in the Strombidce : the mouth is 

 probosciform and extensile ; and the foot, in the typical 

 group, of enormous size. 



(86.) The shells, however, present us with more 

 tangible characters. The base is never prolonged ; 

 although in some mitres ( Tiara) it is contracted : in 

 all others it is truncated, as in the Buccinince, and 

 deeply notched. The truncated base at once separates 

 this family from the TurbinellintB, as there is no in- 

 stance of a volute with an elongated channel. The 

 plaits upon the pillar,, again, are always at the base 

 not in the middle only of the aperture ; although, in 

 the aberrant groups of Oliv a, Ancillaria, and Marginella, 

 they assume peculiar modifications. The proportion of 

 the spire to the aperture varies in almost every genus ; 



