44 



Family 2. COLUMELLATA. 



Shell ; emarginated at the base, toith the colmnella strongly oh- 

 liqiiely plaited. 



The genera of pectinibrancliial gastropods constituting the family Colu- 

 mellata, all included by Linnaeus under the head of Valuta, are mainly 

 characterized by the presence of four or five conspicuous plaits winding 

 obliquely round the columella^ with a notch at the base, or rather front edge 

 of the shell, viewing it in its natural position upon the animal, for the 

 passage of the respiratory siphon. A modification of tliis structure appears 

 also in some genera of Canahfera, as in Turbinella, and Cancellaria ; not 

 only, however, are tlie plaits in that family more limited in number and 

 more feebly developed, but the genera are allied by other characters of 

 greater importance. The Auricula shells are, in like manner, characterized 

 by a plaited columella, but they again are the production of animals dwelling 

 in fresh and stagnant water, whose physical condition is necessarily adapted 

 to the different medium they inhabit"^. 



In reviewing the soft parts of the Columellata it may be observed that 

 they are very much larger and more expansile in some species than in 

 others ; the Marginella have the mantle expanded entirely over the sheU, 

 as in Cuprcea ; in Cyrnhmm the disc is very large and muscular, the shell 

 light and ventricose, wliilst the mantle of that genus, as well as of Voluta, 

 is in some instances partially expanded over the shell. The animal of 

 Mitra, on the other hand, is small, the shell often sohd and ponderous, 

 with a thick fibrous epidermis, and there is no outward expansion of the 

 mantle, whilst the proboscis is capable of extraordinary elongation. 



The genera of this family are extremely rich in species, but of those 

 referred to it by Lamarck and Deshayes, I remove Coliimbella to the family 

 Purpurifera : first, on account of the absence of plaits on the columella, 

 and, secondly, because of its nearer affinity with Purjmra and Ricimda ; 

 in place of tliis a new and interesting genus has to be inserted after Mar- 

 ghiella, founded by M. Deshayes upon a Kttle inhabitant of the Mediter- 

 ranean, under the name of R'mgicida. 



Cymbium. Mitra. Ringicula. 



Voluta. Marginella. 



* Mr. Swainson had a notion that every character in Zoology, however unimportant, is repre- 

 sented in coin])lete analogy throughout the different classes of animals, within very prescribed 

 limits ; he conceived, for example, that the Volutes and Miires represent the Rasorial type 

 among Birds, the JJngvlata among Quadrupeds, and the Thysanura among Insects. These flights 

 of analogy he proposed to exhibit in circles ; and they revolved in his imagination in such mys- 

 tical order as to reveal the most incomprehensible affinities. 



