SUB-ORDER B PTEROPODA 489 
It manifestly cannot be denied that Conularias and Hyolithes in particular, as 
regards size, shell structure, and probably also conditions of existence, differed con- 
siderably from recent Pteropods. But in spite of the differences so strongly 
emphasised by Pelseneer, the fact remains that of all shell-covered organisins, they 
approach the Pteropods most nearly, and cannot with propriety be referred to any 
other group of the Mollusca. 
Family 1. Limacinidae. Gray. 
Shell thin, spiral, sinistral, with vitreous, paucispiral 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, 
contains similar forms from the Oligocene of San Domingo. 
Family 2. Cavoliniidae. Fischer. 
Shell symmetrical, thin, vitreous, ventricose, pyramidal, or conically tubiform, but not 
spiral. Cretaceous to Recent. 
Cavolinia, Gioeni (Hyalaea, Lam.; Gamopleura, Bellardi), (Fig. 1020). Shell 
globose, laterally keeled and sht, acuminate pos- 
teriorly ; composed of two unequally arched pieces, 
one of which projects helmet-like above the other. 
Recent, and fossil in the Italian Miocene and 
Pliocene. 
Clio, Linn. (Cleodora, Péron and Lesueur ; 
Balantium, Benson ; Flabellum, Poculina, Bellardi), 
(Fig. 1021). Shell somewhat angular, compressed Fic. 1020. 
dorso-ventrally, with lateral keels. A crest or rib _ 4, Cavolinia (Hyalaea) tridentata, Forsk. 
generally extends longitudinally along the back, and fey Ceres ees ee ee 
usually projects. Upper Cretaceous to Recent. <A 
common fossil in the Pliocene of Monte Mario, near Rome, and the vicinity of Messina 
and Turin; also in the Oligocene of the Mayence Basin, and in the English Crag. 


Fic. 1022. 
Fic. 1021. A, Styliola recta, Lesueur. Recent (after 
A, Cleodora pyramidata, Linn. Pliocene; Monte Adams). , B, Styliola_striatula, Novak. De- 
Mario, near Rome. 8B, Balantium recurvun, A. vonian (Btage H); Hlubocep, Bohemia. 4/). 
Adams. Recent. Animal with shell (after Adams). C, Styliola clavulus, Barr. Devonian (Etage H); 
C, Vaginella depressa, Daudin (Cleodora strangulata, Hostin, near Prague, Bohemia. Several in- 
Desh.). Miocene; Dax, near Bordeaux. dividuals on slate-fragment. 1/). 
-Sub-genus: StyZiola, Lesueur (Creseis, Rang ; Crisia, Menke), (Fig. 1022). Shell conical, 
