266 



THE LAMELLIBRANCHIA 



c.o 



Genera Kellya, Turton ; mantle with two sutures and three orifices, the 

 pedal orifice being the middle and not the anterior of the three (Fig. 187) ; 

 foot linguiform ; the external gill-plate with a reflected lamella ; British. 

 Lepton, Turton; mantle with a single suture ; the mantle edges provided 

 with tentacles ; foot with a plantar ventral surface ; commensal ; British. 

 Lasaea, Leach ; a single pallial suture ; the foot linguiform and elongated ; 

 the external gill -plate not reflected (Fig. 206, G) ; British. Erycina, 

 Lamarck ; fossil from the Tertiary. Pythina, Hinds. Scacchia, Philippi. 

 Sportella, Deshayes. Cyamium, Philippi. FAMILY 17. GALEOMMIDAE, 

 Gray. Mantle more or less completely reflected over the shell Foot 

 well developed, generally byssiferous. Shell thin, gaping ; the adductor 

 muscles much reduced. Genera Galeomma, Turton ; shell incompletely 

 covered by the mantle ; a single pallial suture ; a large azygos anterior 

 pallial tentacle, and a short anal siphon present. A byssal groove in the 

 foot ; British. Scintilla, Deshayes. Hindsiella, Stoliczka. Ephippo- 

 donta, Tate ; shell internal ; a single pallial suture ; gills with two gill- 

 plates ; commensal with the shrimp 

 A Axius; Australian. The three following 



*^ genera with an internal shell probably 



belong to this family : Chlamydoconcha, 

 Dall ; two gill-plates ; a pallial suture ; 

 an anterior orifice leading into a caecum ; 

 no adductor muscles ; sexes separate ; 

 from California (Fig. 239). Scioberetia, 

 Bernard ; gills with a single gill-plate ; 

 a single pallial suture ; foot large, elon- 

 gated, with a byssal groove ; hermaphro- 

 dite and commensal with a Spatangid, 

 Triphylua; from Cape Horn. Entovalva, 

 Voeltzkow (Fig. 240); mantle fairly 

 open, with a single suture; foot large, 

 with a posterior pore ; hermaphrodite 

 and incubatory ; endoparasitic in Synapta 

 ( = Syiiapticola, Malard), Madagascar and 

 Atlantic. FAMILY 18. KELLYELLIDAE, 

 Fischer. Mantle with a single pallial 

 suture ; anal orifice with a very short 

 siphon ; foot elongated ; gills with two 

 unequal plates. Shell ovoid ; the liga- 

 ment external ; the anterior lateral 

 hinge tooth below the cardinal tooth. 

 Genera Kellyella, Sars. Turtonia, 



Forbes and Hanley ; British. Allopagus, Stoliczka ; fossil from the Eocene. 

 Lutetia, Deshayes ; fossil from the Eocene. FAMILY 19. CYRENIDAE, 

 Gray. Mantle with two siphons, which are more or less intimately united 

 together and have papillose orifices. The sexes separate. Shell with 

 external ligament; the pallial line usually with a sinus. Freshwater 

 forms. Genera Cyrena, Lamarck. Corbicula, Megerle. Batissa, Gray. 

 Velorita, Gray. Galatea, Bruguiere. Fischeria, Bernardi. FAMILY 20. 



Fio. 230. 



CMamydoconcha orcutti, Dall. A, dor- 

 nal aspect ; B, left-side view, a.o, anal 

 orifice ; c.o, caecal orifice ; /, foot ; pa, 

 mantle. (After Bernard.) 



