168 



THE GASTROPODA 



Posteriorly the mantle forms a large " pallial lobe " under the pallial 

 aperture (Figs. 98, i.l ; 148, I). The stomach is generally provided with 

 chitinous, or even calcined, masticatory plates (Fig. 76, m.p). The visceral 

 commissure is fairly long, except in such specialised forms as Runcina, 

 Lobiger, and the Thecosomata (Fig. 60, n.s). The hermaphrodite genital 

 aperture is connected with the penis by a ciliated groove, except in Actaeon 

 (Fig. 148), Lobiger, and Cavolinia longirostris, in which the spermiduct is a 

 closed tube. The Bullomorpha are swimmers or burrowers. 



FAMILY 1. ACTAEONIDAE, Adams. Cephalic shield bifid posteriorly; 

 the margins of the foot slightly developed ; the genital ducts diaulic ; the 

 visceral commissure streptoneurous ; the shell thick, with a prominent 

 spire and elongated aperture ; columella generally folded ; a corneous 

 paucispiral operculum. Genera Actaeon, Montfort ; British (Fig. 148). 

 Solidula, Fischer von Waldheim. Tornatellcea, Conrad ; extinct. Triplaca, 

 Tate ; from the Eocene. Adelactaeon, Cossmann. Actaeonina, d'Orbigny ; 

 Carboniferous to recent. Bullina, Ferussac. Bullinula, Beck. Actaeo- 



PlG. 147. 



Acera bullata, swimming, 

 left-side view. /, fin (foot) ; 

 m, mouth ; sh, shell. (After 

 Guiart.) 



FIG. 148. 



Actaeon tornatilis, removed from its shell, right-side view. 

 I, inferior lobe of tho mantle ; II, glandular hollow pallial 

 appendage (extending to the first whorls); III, pallial (hypo- 

 branchial) gland ; IV, opening of the pallial cavity ; V, eye and 

 cephalic hood ; VI, penis. 



nella, d'Orbigny ; from 

 the Cretaceous. Vol- 

 varia, Lamarck ; Eocene. 

 Odostomiopsis, Thiele. 

 FAMILY 2. RINGICU- 

 LIDAE, Fischer. Cephalic disc enlarged anteriorly and forming an open tube 

 posteriorly ; shell external, thick, with a prominent spire ; no operculum. 

 Genera Ringicula, Deshayes. Pugnus, Hedley. Cinulia, Gray ; from the 

 Cretaceous. Avellana, d'Orbigny ; from the Cretaceous. Fortisia, Bayan ; 

 from the Eocene. FAMILY 3. TORXATINIDAE, Fischer. Margins of the 

 foot not prominent ; no raclula ; shell external with inconspicuous spire ; 

 no operculum. Genera Tornatina, Adams ; British. Retusa, Brown. 

 Volvula, Adams. FAMILY 4. SCAPHANDRIDAE, Fischer. Cephalic shield 

 short, truncated posteriorly ; eyes deeply imbedded ; three calcareous 

 stomachal plates, two broad and paired, one narrow and azygos ; shell 

 external, with reduced spire. Genera Scaphcmder, Montfort ; British. 

 Sabatia, Bellardi ; Eocene. Atys, Montfort. Smaragdinella, Adams. 

 Cylichna, Loven ; British. Amphisphyra, Loven ; British. FAMILY 5. 

 BULLIDAE, d'Orbigny. Margins of the foot well developed ; eyes super- 

 ficial ; three chitinous- stomachal plates ; shell external, with reduced 



