CONCHIFERA. 



255 



fervid mthe tanks. Sub -genera. Gryphcea, 

 Lamarek. G. incurva, Sby (section) fig. 

 178. Free, or very sliglitly attached ; left 

 valve \Nith a prominent, incurved umbo ; 

 right valve small, concave. Fossil, 30 sp. 

 Lias — Chalk. Europe, India. 



Exogyra, Sby. E. coniea, PI. XVI. 

 fig. 3. Shell ehama-shaped, attached by 



the left valve ; umbones sub-spiral, turned Fig. 178. Gryphcea. 



to the posterior side (i. e. reversed) ; right valve opercular. Fossil, 40 sp. 

 L. Oolite — Chalk. U. States ; Europe. 



Anomia, L. 



Ftym. Anomios, unequal. Ex. A. Achaeus, PI. XVI. fig. 3, 



Syn. Fenestrella, Bolten ; Cepa, Humph. Aenigma, Koch. 



Shell sub-orbicular, very variable, translucent, and slightly pearly 

 within, attached by a plug passing through a hole or notch in the right 

 valve: upper valve convex, smooth, lamellar or striated; interior with a 

 sub-marginal cartilage-pit, and four muscular impressions, 3 sub-central, and 

 one in front of the cartilage (see fig. 175, p. 249) : lower valve concave, 

 with a deep, rounded notch in front of the cartilage process ; disk with a 

 single (adductor) impression. 



Animal with the mantle open, its margins with a short double fringe ; 

 lips membranous ; palpi elongated, fixed, striated on both sides ; gills 2 on 

 each side, united posteriorly, the outer laminse incomplete and free ; foot small, 

 •cylindrical, subsidiary to a lamellar and more or less calcified byssal plug, 

 attached to the upper valve by three muscles ; adductor muscle behind the 

 byssal muscles, small, composed of two elements ; sexes distinct ; ovary ex- 

 tending into the substance of the lower mantle-lobe 



In A. pertioides, from California, there is an anterior {pedal) muscular 

 impression in both valves. 



" There is no relationship of affiniiy between Anomia and Terebratula, 

 l)ut only a resemblance through formal analogy ; the parts which seem iden- 

 tical are not homologous." (Forbes). 



The Anomise are found attached to oysters and other shells, and frequently 

 acquire the form of the surfaces with which their growing margins are in 

 contact. They are not edible. 



Bistr. 20 sp. N. America, Brit. Black Sea, India, Australia, W, America, 

 Icy sea. Low-water — 100 fms. 



Fossil, 30 sp. Oolite — , Chile, U. States, Europe. 



Sub-genera. Placimomia (Cumingii) Broderip. Syn. Pododesmus, Phil. 

 P. macroschisma, PI. XVI. fig. 4. Upper valve with only two muscular 

 impressions ; the pedal scar radiately striated ; the byssal plug is often fixed 



N 



