560 



MOLLUSCA 



PHYLUM VI 



columella!' boi^der sliglitly twisted, with two or three small oblique plaits anteriorly ; 

 sometimes uml)ilicate. Cretaceous to Recent. 



Pisanella v. Koeneii. Oligocene. Peristernia Miirch ; Leucozonia Gray. Tertiary 

 and Recent. 



Family 6. Vasidae Adams. (Turbinellidae auct.). 



Shell similar to those of the preceding family, hut with strong, horizontal columellar 

 folds. Tertiary and Recent. 



Xancus Bolt. (Turhinella Lam. ; Mazza Adams ; Mazzalina Conrad). Thick- 

 shelled, ovate -conical, smooth; spire short and Idunt, body whorl large; canal 

 straight, elongated. Eocene to Recent. 



Vasum Link {Cynodonta Schum.). Shell lieavy, strongly sculptured, often s^iinose, 

 with short canal. Tertiary and Recent. 



Family 7. Volutidae Gray. 



Shell thick, ovate to fusiform, didl or lustrous. Spire short or long, body whorl large. 

 Aperture elongated, with a short canal or notch; inner lip tvith columellar folds. Oper- 

 culum usually absent. Cretaceous to Recent. 



This family, as here defined, contains genera distributed by malacologists amongst 



several families — Marginellidae, Mitridae and 

 Volutidae — all of ^^'hich are characterised by the 

 strong development of columellar folds ; but it is 

 likely that this structure originated independently 

 in several I)hyla at intervals remote from one 

 anotlier. The initiation of well-marked genera 

 with Volutoid plaits occurred in the Cretaceous. 

 Subsequently their number increased, and a great 

 many generic tyjies became differentiated. The 

 phylogeny of Tertiary and Recent forms has been 

 ably worked out by Dall.^ 



Marginella Lam. (Fig. 1031). Shell oval or 

 oblong, smooth, glistening. Spire short ; aperture 

 narrow, slightly canaliculate anteriorly. Columella 

 with three or four oblique folds of about equal 

 size; outer margin frequently thickened and dentate. 

 Tertiary and Recent. 



Mitra Lam. (Fig. 1032). Fusiform to elongate- 

 oval, solid ; spire high, acuminate ; aperture narrow, 

 channelled anteriorly. Columella with numerous 

 oblique folds, the posterior plaits 



being often the strongest. Outer mai'gin commonly thickened, and 



smootli internally. Abundant in the Tertiary and Recent. 



Turricida Adams. Like the last, biit shell transversely ribbed. 



Cretaceous to Recent. 



Strigatella Swains. (Fig. 1033) ; Cylindromitra Fischer {Cylindra 



Schum.) ; Imbricaria Schum. ; Volutomitra Gray ; Perplicaria Dall. 



Tertiary and Recent. 



Lyria Gray (Fig. 1034). Elongate -oval, transversely ril)l)ed. 



Aperture narrow. Columella anteriorly with two much compressed 



Fig. 1031. 



Marginella crassula 

 Desh. Calcaire Gros- 

 sier ; Chaumont, near 

 Paris. 2/i. 



Pio. 1032. 



Mitra fusiformU 

 Brocchi. Plio- 



cene ; Rhodes. 



1038. 



' Bull. Museum Comp. Zoology, vol. xviii., 1889 ; Proc. U.S. Nat. 

 Museum, vol. xii., 1890, Trans. Wagner Free Inst. Sei. Philad., vol. iii., 1890. 



Strigatella InhmtnUi 

 (Ijam.). Eocene; 

 Grignon, near Paris. 



