Invertebrate Gallery of the Indian Museum. 119 



able in being cylindrical and in being divided into two 

 portions — an after portion which carries the horny oper- 

 culum, and a front portion on which the animal hops. 



nth Family, Naticidae [Cases 140Y — 141 A]. 



This is a (large and geologically ancient family of 

 predaceous marine mollusks. The animals have a small 

 head, and an enormous foot for burrowing, and they are 

 usually blind. The shells generally have the last whorl 

 of great size and the spire small, and are either globose 

 or ear-shaped : the operculum is either w^ell developed 

 and stony, or horny and rudimentary. The Naticidge are 

 of universal distribution and are very abundant in tropical 

 seas, 



i2th Family, Marsenidge [Case 141 A]. 



A small family of carnivorous marine mollusks in 

 many respects resembling the Naticidx. The shells, 

 which are very fragile and are often covered with an 

 epidermis, or are sometimes hidden by the foot, resemble 

 those of Sigaretus among the Naticidx^ but have no 

 operculum. 



13th Family^ Acmseldae [Case 141 B]. 



The Acmasidx are known as "False Limpets" from 

 the resemblance of their shell to that of the Limpets. The 

 animal, however, differs from the Limpet in having a single 

 true gill-plume on the right side of the neck ; whereas in 

 the true Limpet the gill-plumes are minute rudiments 

 placed symmetrically one on each side of the neck, and 

 the functional gill, as may be observed in the spirit speci- 

 men above Case 128, consists of a fringe of filaments 

 hanging from the inner surface of the mantle throughout 

 its whole circumference. The Acmgeidce are widely 



