570 



MOLLUSCA 



PHYLUM VI 



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

 large group. 



Family 1. Limacinidae Gray. 



Shell thin, spiral, sinistral, with vüreous, 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 Planorhella Gabb 

 comprises similar forms from the Oligocene of San Domingo. 



Family 2. Oavoliniidae Fischer. 



Shell symmetrical, thin, vüreous, ventricose, pyramidal, or conically tubiform, but not 

 Spiral. Cretaceous to Recent. 



GavoUna Abildgaard {Hyalaea Lam. ; Gamopleura Bellardi) (Fig. 1069). Shell 



globose, laterally keeled and slit, acuminate pos- 

 teriorly ; composed of two unequally arched pieces, 

 one of wliich projects helmet-like above the otlier. 

 Recent, and fossil in the Italian Miocene and 

 Pliocene. 



Glio Linnaeus (Gleodora Peron and Lesueur ; 

 Balantium Benson ; Flabellum, Poculina Bellardi) 

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

 pressed dorso-ventrally, with lateral keels, A crest 

 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 

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

 the English Crag. 



Fig. 1069. 

 A, Cavolina (Hyalaea) tridentata Forsk. 

 Recent. B, C, C. (Gamopleura) taurinensis 

 Sism. Miocene ; Turin, Italy. 



Fig. 1070. 



A, Clio (nieodora't mimmhintn t ,•«„ -dt ^' ^"""^s^^s recta Lesueur. Recent (after 



MonteMaroSrRomrR %/?«•; ^ '^^^"6 ; A^lams). B, Styliola striatulaNova\^. Devonian 



cnr.L A idam? ge^ent. i^iSÄhellTaV;; (f ^'^f H) ; Hlubocep, Boheniia. 3/,. C, Crese^s 



Adams). C, Vngindla depr^.Ta h^^^ '''''"'^;'' ^^"v, ?«^?nian (Etage H) ; Hostin, 



strang^latam.lrS Mioceni'rSx^nJar BoEx TtlSent "''i/r'' "'""' -dividuals on 



buTflthtiv ^ntl ITl? T ff »t^y «triated ; dorsal groove not parallel to axis of the shell 

 1 ne enSonrnnrT n ° / • ^'' ^''^■''''\ «^t^'e»^ity (wlnch ends in a rostrum) in the median 

 line embryonic portion ends in a pomted apex. Tertiary and Recent. 



apeSlh-cuSr"' ^ ^' ^'^- ^'"^''^' '''^^ ^^"^^°"^ protoconch, no dorsal groove, 



