570 



MOLLUSCA 



PHYLUM VI 



same stem as the Pteropoda, and their natural association with the latter in a single 

 lai-ge group. 



Family 1. Limacinidae Gray. 



Shell thin, spiral, sinistral, with vitreous, patocispiral operculum. Tertiary and 

 Recent. 



The genus Limacina Lam. {Spirialis Eyd. and Soul. ; Embolus Jeffreys), is of 

 sporadic occurrence in the Tertiary (Eocene and Pliocene). Valvatina Watelet, 

 includes flat sinistral shells from the Calcaire Grossier of Paris, and Planorbella Gabb 

 comprises similar forms from the Oligocene of San Domingo. 



Family 2. Cavoliniidae Fischer. 



Shell symmetrical, thin, vitreous, ventricose, pyramidal, or conically tuhiform,, hut not 

 spiral. Cretaceous to Recent. 



Gavolina Abildgaard (Hyalaea Lam. ; GamojAeura Bellardi) (Fig. 1069). Shell 



globose, laterally keeled and slit, acuminate pos- 

 teriorly ; composed of two unequally arched pieces, 

 one of which projects helmet-like above the other. 

 Recent, and fossil in the Italian IMiocene and 

 Pliocene. 



Clio Linnaeus {Glcodora Peron and Lesueur ; 

 Balantium Benson ; Flahellum., Poculina Bellardi) 

 (Fig. 1070, A, B). Shell somewhat angular, com- 



FiG. 1060. 



A, Carnlinct {Hyalaea) t 

 lecent. B, C, 

 Sism. Miocene ; Turin, Italy. 



.-a m) tridrntata Porsk. pressed dorso-ventrally, with lateral keels. A crest 



Recent. B, V, (J. (Gamopleura) taurmensis ., ■■, -i •. -f ]• n ^ „ f1 <a 



or rib generally extends longitudinally along the 

 back, and usually projects. Upper Cretaceous to 

 Recent. A common fossil in the Pliocene of Monte Mario, near Rome, and in the 

 vicinity of Messina and Turin ; also in the Oligocene of the Mayence Basin, and in 



the English Crag. 



Fiii. 1070. 



A, Clin (Claoilora) pyramidata Linn. Pliocene ; 

 Monte Mario near Rome. B, Clio (Balantii(.m) rc- 

 mrniiii A. Adams. Recent. Animal with .shell (after 

 Adams). C, VaijinrUa drpr(t<><a Daudin (Cleodnra 

 stmnguliitn Desh.). Miocene; Dax, near Bordeaux. 



Pig. ion. 



A, Crc.teis rrctn Lesueur. Recent (after 

 Ailanis). B, Styliola striatuhi. Novak. Devonian 

 (Etatie H) ; Hlubocep, Bohenjia. 3/,. C, Creseis 

 clavidnn Barr. Devonian (Etaue H) ; Ilostin, 

 near Prague, Bohemia. Several individuals on 

 slate-fragment. Vi- 



Subgenus: Creseis Rang [Crisia Menko) (Fig. 1071, A, C). Shell conical, straight, 

 elongated ; surface smooth or faintly striated ; dorsal groove not parallel to axis of the sliell, 

 but slightly sjnral, with only the anterior extremity (which ends in a rostrum) in the median 

 lino ; enibryoni(! portion ends in a iwinted a]>e\. Tertiary and Recent. 



Styliola Lesueur (Fig. 1071 H). Conical, with bulbous iirotoconeli, no dorsal groove, 

 aperture circular. 



