MOLLUSCA. 



83 



CLASS III. PTEROPODA. 



ORDER I. GYMNOSOMATA. 



Fam. Cliidae. Clio, Pneumodermon. 



ORDER II. THECOSOMATA. 



Fam. a. Hyaleidse. Hyalea, Cleodora. 



Fam. Z>. *Hyolithidse. Hyolithes (Theca). 



Fam. c. Cymbuliidse. Cymbulia. 



Fam. d. Limacinidse. Limacina, Spirialis. 



(Eang et Souleyet, Histoire naturelle des Mollusques Pteropodes, Paris, 

 1852 ; Gegenbaur, Untersuchungen iiber die Pteropodtn und Heteropoden, 

 Leipzig, 1853 ; Krohn, Beitrage zur Entwickelungsgeschichte der Pteropoden 

 und Heteropoden, Leipzig, 1860 ; Barrande, Pteropodes, in the ' Systeme 

 Sihirien du Centre de la Boheme,' 1867.) 



Pig. 75. Pteropoda. A, Spirialis rostralis B, Pneumodermon violaceum. c, Heterofusiis 

 bulimirurides. All enlarged, e, Epipodia or fins ; t, Tentacles. D, Larva of Cleodora lanceo- 

 lata, greatly enlarged (after Fol) : v, Velum ; o, Mouth ; <e, Gullet ; g, Stomach ; i, Intestine ; 

 nn, ColumeUar muscle; s, Shell; ti, Yolk-sac. 



