34 



de Conchyliologie, 261, I860, gave a more scientific synopsis of 

 the species, increasing their number to 31 ; finally, Sowerby 

 (Thesaurus Concli3<liorum, v, 1882) reduced them to 11. 



The following sections of Morch have very slight value. I 

 include the first and second in a single species, whilst the other 

 three ma}' divide two species between them. 

 Section IODES (Leach), Gray, 1847. 



Solid, depressed conical, last whorl obtusely cariuate. Vivi- 

 parous. I. BRITANNICA, Leach. 

 Section ACHATES (Gistel), Morch, 1860. 



Shell thin, acutely carinated. Oviparous, marsupial. Proboscis 

 inflated. I. FRAGILIS, Lam. 

 Section IANTHINA (Bolten, 1798)., Morch, 1860. 



Globose, with deep suture, columella produced, aperture 

 sinuated below. Oviparous, marsupial, proboscis cylindrical, 

 branchia protruding. I. NITENS, Menke. 

 Section AMETHISTINA (Schinz, 1825), Morch, 1860. 



Like the last, but aperture rounded below. I. PALLIDA, 

 Harvey. 

 Section IODINA, Morch, 1860. 



Costulate, lip incised. Oviparous, marsupial. I. EXiGUA,Lam. 



The lanthinse, or Purple Snails, are gregarious and very 

 abundant on the surface of the ocean where the water is deep 

 and similar in color to themselves. They live on Velellae, Por- 

 pitae, Physalii-e and other soft animals, usually of similar violet 

 coloring; finally a bluish crustacean dwells on their float. Ac- 

 cording to Dr. Coates they sometimes eat their own species. 

 The float is readily, even spontaneously detached, and is often 

 encountered in numbers, apart from the animal. If its vesicles 

 are punctured the air escapes and the animal falls to the bottom, 

 from which it appears unable to ascend, and is supposed to 

 perish. The stem of the float is attached to the posterior part 

 of the foot ; the anterior part of the foot becomes tubular by the 

 turning over of its margins, and when protruded from the water, 

 encloses a bubble of air, which, being enveloped in a mucous 

 secretion, is added to the anterior portion of the float. There 

 has been much written upon the homologies of this raft ; the 

 accepted opinion compares it with the byssus of lamcllibranchs. 



