380 MOLLUSC A. 



not passing through the heart. Many groups are recognized, based upon 

 the structure of the lingual ribbon. Of the thousands of species only a 

 few groups can be included here. KHACIIIGLOSSA ; siphonostornate, 

 predatory. MURICID.E (Murex, Purpura* Urosalpinx*) have an anal 

 gland secreting a substance first colorless, turning to purple by exposure 

 to air. The Tynan purple was produced by Murex trunculus. Urosalpinx 

 cinereus* drills into oysters. BUCCINID.E, whelks, VOLUTID^E, and OLIVID^E 

 belong here. TOXIGLOSSA ; CONID^E, with large oesophageal poison 

 gland, some species producing severe wounds. Conus, tropical; Bele.* 

 T^ENIOGLOSSA ; NATICID.E, Neverita* and Lunatia,* common snail of 

 Atlantic coast, their egg-masses being the familiar sand saucers. LIT- 

 TORINID.E ; periwinkles. CYPR^EID^B, cowries; Cyprcea moneta of India is 

 used as money in Africa. AMPULLA RID^E; amphibious, part of branchial 

 cavity acting as lung, part containing ctenidium. PALUDINID^E, fresh 

 water. CYCLOSTOMID.E, tropical terrestrial forms, the mantle cavity a 

 lung. 



HETEROPODA. In all details of gills, genitalia, heart, and nervous- 

 system these are true Pectinibranchs, but from an exclusively pelagic life 

 have acquired peculiar modifications. As in most pelagic animals the 

 body is gelatinous and transparent. The head is elongate, and the body is- 

 enlarged so that usually it cannot be retracted into the shell. Most char- 

 acteristic is the division of the foot into pro- and metapodium (fig. 375), the 



FIG. 375. Carinaria mediterranea (after Gegenbaur), shell removed. A, metapodium ; 

 a, anus ; ar, aorta ; #, visceral sac ; ftr, branchiae, the heart above ; 'if, vas def- 

 erens ; o, mouth ; oc, eye with tentacle ; 05, oasophagus : p. propodium : ns. penis ; 

 I, II, III, cerebral, pedal, and visceral ganglia. 



latter forming a tail-like elongation of the body. The propodium is verti- 

 cally flattened and by its undulations serves as a swimming organ. The 

 Heteropoda are predaceous and extremely voracious ; they swim back 

 downwards. The ATLANTID^ can completely withdraw into the shell and 

 close it with an operculum ; the CARINARIHLE (fig. 375) have a shell which 

 scarcely covers the visceral complex ; the PTEROTRACHEID.E have no shells. 



