MOLLUSCS. 



327 



Sub-Order II. — Rhachiglossa. 



The Ehaehiglossa are all j)i'eilaceous marine snails with well-developed proboscis 

 and a respiratory siphon, which, wheti the animal is extended, lies in a iiotcli in the 

 aperture or in a long, more or less tubular canal of the shell. The tongue is long and 

 small, and bears at the most but three teeth in a transverse row, one rhachidian and 

 one lateral on either side, the latter being occasionally reduced to mere hooks, or, as 

 in the ease of the Volutidse, they have entirely disapjieared, and the central or rhachi- 

 dian teeth alone remain. All are predacious and carnivorous. 



We have just referred to one of the characters of the VolutidyE, liut now we 

 may give some others derived from other parts. The shell is thick and heavy, and 

 the spire is short, rising but little above the body 

 whorl. The anterior margin or base of the aper- 

 ture is deeply notched for the respiratory siphon, 

 wliile the columella bears strong spiral plaits or 

 folds. The eyes are placed at the base of the 

 tentacles, and the foot is large and broad. Tlie 

 typical genus is J^olufa, in which the spire is 

 short, the mouth wide, and the first fold on the 

 columella is the largest. The species are largely 

 fi-om the Indo-Pacific region, although some are 

 found in other seas. One of the most interesting 

 siiecies is that figured. It derives its specific 

 name, ?»itsica, from a number of fine dark lines 

 interspersed with blotches, which follow the 

 whorls of the shell and bear no distant resem- 

 blance to written music. In some the similarity 

 is more marked than in the specimen figured. 

 This species presents an exception to most of 

 the Volutes, in having a small operculum de- 

 veloped. It comes from the West Indies. 



As an example of the forms from tlie eastern seas we may mention the beautifully 

 shaped species from the Philippine Islands, which, from its diadem of spines and its 

 size, well deserves the name, Valuta imperiali.s, which science has gi\en it. It is 

 common in collections. The last species which we can mention is the rare Voluta 

 JiiJio/iia, or, as it is called by dealers, the peacock-tail volute. The figure represents 

 the shell of the natural size; it is white, spotted with orange. For many years it was 

 considered among the rarest of shells, specimens having been sold for about two 

 hundred dollars, and no later than 1876 a specimen brought fifty dollars. Recently 

 quite a number have been brought from the West Indies, and now they c^an be bought 

 of the dealers for eight or ten dollars. 



Most of the Volutidae are ovo-viviparous ; that is, they bring forth living young : 

 but some, if not all, of the genus Valuta lay eggs, which are enveloped in a jierfectly 

 transitarent, corneous cori)uscle half as large as the parent. Cymhhim and JA/o bring 

 forth their young alive, a brood containing four or more individuals. 



In Marf/inella we have some two hundred species of small, polished oval shells 

 with the respiratory notch small. Most of them are brightly colored, and in life the 



Fig. 40C. — Voluta miisica. 



