VII 



MOLL USOA—S YSTEMA TIC RE VIE W 



-Parmoplwnis), Pkurotomaridcc (Pkurotomaria, Sdsmrclla, Polytrcmaria), Bellero- 

 phontidce (exclusively fossil). 



h. Azygobranchia. — One gill, homologous with the left gill of the Zeugo- 

 branchia. Right auricle ending blindly. Heart perforated by the rectum. Fam. 

 Turhonidcs, rad. ooO.(5.1.5.)0.<» , TrocUdcc (Fig. 3) Stoviatiidce, Neritopsida; rad. 

 a>l.(2.0.2.)l.co , marine, Neritidm, rad. ool.(3.1.3.)l.oo (marine, but along the shore 

 able to live out of water), Keritinix (marine and fresh-water). The Sydrocoenidce, rad. 

 ool.(l.l.l.)l.co, and ffelicinidce, rad. co.l.(4.1.4.)l.oo , have no gills but a lun" 

 resembling that of the Pulmonata. The ffelicinidce are terrestrial. 



c. Doooglossa. — Heart with one auricle, and not perforated by the rectum. Left 

 kidney shifted to the right side of the pericardium. Visceral dome and shell 

 secondarily symmetrical, the latter usually cup-like. Operculum wantino-. Marine. 



Fir,. 6.— Phoras exutus (after Lankester). o, Proboscidal snout or rostrum ; b, tentaclB ; 

 0, eye ; d, foot ; e, metapodiuui with operculum/. 



1. Left true ctenidium present. Acmaeidce, vad. 1.2.(1. 0.1.)2.1.; with numerous 

 accessory gills in the mantle furrow: Scurria ; — without such gills: Aanaea 

 (Teetura). 



2. True ctenidia altogether wanting, accessory gills very numerous in the mantle 

 furrow.— Fam. Patellidce (Fig. 4), rad. 3.1.(2.0.2. )1.3. 



3. Neither ctenidia nor accessory gills found (Lepetidce), rad. 2.0.1.0.2. 



Sub-Order 2. Monotocardia (Peotinibranchia). 



Heart with one auricle. A single true ctenidium feathered on one side, the point 

 not projecting freely (except in Valvata). Pedal nerve trunks a jare exception, pedal 

 ganglia the rule. Only one kidney. Siphon and penis generally present. Epi- 

 podium weakly developed or wanting. The Monotocardia are very numerous and 

 are chiefly marine. 



a. Architaenioglossa. — Pedal nerve trunks. In Cypraea (and in other forms ?) a 

 rudiment of the right auricle persists. Fam. Oypraeidce, rad. 3.1.1.1.3, Paludinidm 

 (fresh-water), OyclopJioridM (terrestrial, pulmonate). 



