EULAMELLIBRANCHIATA. 347 



generally with emerald -green pallial eyes; outer gill-filaments free. Some are 

 fixed by one valve, and some can swim by opening and shutting their valves. 

 Pecten Lam. ; Pedum Drug. ; Hinnites Defr. ; Spondylus L. ; Lima Bruguiere. 

 Pectens, the Scollops are edible ; they swim by flapping their shells ; Spondylus 

 is attached by one valve. ^/ 



The Dimyidae are allied here. 



Order 4. EULAMELLIBRANCHIATA. 



Interftlamentar and interlamellar (vascular) concrescences always present. 

 The mantle-lobes are connected together either by direct fusion or by the 

 gills ; the genital glands have independent external openings. 



Sub-order 1. SUBMYTILACEA. 



Mantle generally widely open, usually with one fusion ; usually without 

 siphons. 



Fam. 1. Carditidae. A single mantle-fusion ; foot keeled, often byssiferous. 

 Cardita Bruguiere. The families Astartidae and Crassatellidae are allied here. 



Fam. 2. Cyprinidae. Foot long and bent ; two mantle-fusions ; papillose 

 orifices ; umbones often spiral. Cyprina Lam. ; Isocardia Lam. 



Fam. 3. Lucinidae. The external gill sometimes absent ; foot vermiform 

 without byssus. Lucina Bruguiere (Fig. 250 bis) ; Axinus Sowerby ; Montacuta 

 Turton ; Corbis Cuv. ; Diplodonta Br. ; Ungulina Daudet. 



Fam. 4. Erycinidae. Foot byssiferous or with ventral surface enlarged. 

 Kellya Turton ; Lepton Turton ; Lasaea Leach. 



Fam. 5. Galeommidae. Foot with furrow, mantle edges reflected over the 

 shell. Galeomma Turton ; Ephipodonta Tate. Chlamydoconcha Dall without 

 adductor muscles, and Scioberetia Bernard with only one gill on each side, have 

 an internal shell and are allied here. 



Fam. 6. Cyrenidae. Foot non-byssiferous ; two siphons usually not united ; 

 hermaphrodite, viviparous, fluviatile. Cyclas Bruguiere ; Pisidium PfeifFer, 

 siphons united ; Galatea Brug. ; Corbicula Mlilhf. 



Fam. 7. Unionidae. Fresh-water mussels. Foot long, compressed, without 

 byssus. Anodonta Lamarck (Fig. 257) ; A. cygnea Lam., in ponds ; A. anatina 

 L., in rivers and brooks; Unio Philipsson (Fig. 254); Margaritana Schum., 

 river pearl-mussels ; Mycetopus d' Orb. , America. Mutela Scop. , and Pliodon 

 Conrad, Africa, are allied here. 



Fam. 8. Aetheriidae. Fluviatile forms without foot, usually fixed by one 

 valve. Aetheria Lamck., Africa. 



Fam. 9. Dreissenidae. Foot cylindrical, byssiferous, two siphons. Dreis- 

 sena v. Ben., fresh-water. 



Sub-order 2. TELLINACEA. 



Mantle well open ; gills smooth ; siphons well developed, separate ; foot 

 compressed, elongated ; palps large. 



Fam. 10. Tellinidae. External gill directed dorsally; siphons much elongated. 

 Tellina L. ; Scrobicularia Schumacher ; Semele Schum. ; Gastrana Schum. 



Fam. 11. Donacidae. External gill directed ventrally ; siphons separated. 

 Donax L. 



Fam. 12. Mactridae. External gill directed ventrally; siphons united. 

 Maclra L., clams (Fig. 251). 



