486 MANUAL OF TITE MOLLTJSCA. 



Suh-genera. ? Am,phrchcena,'P'hi[. A. Kindermannl, California. 

 Shell oblong, nearly equilateral, gaping at each end ; teeth -| ; 

 ligament external, pallial line sinuated. 



IpMgenia, Schum. (Capsa, Lam., 1818, not 1801, Donacma, 

 Per.) I. Brasiliensis, PI. XXI.. Fig. 20. Shell nearly equi- 

 lateral, smooth; hinge -teeth 2.2, one bifid, the other minute; 

 laterals remote, obsolete in the left valve ; margins smooth. 

 Distribution, 5 species. West Indies, Brazil, "West Africa, Pacific, 

 Central America. Inhabits e«tuaries. /. ventricosa, Deshayes, 

 is rayed like Galatea, and has its beaks eroded. 



? Isodonta (Deshayesii). Buv. Bull. Soc. Geol. Oolite. 

 France, England. 



Galatea, Bruguiere. 



Synonyms, Egeria, Eoissy. Potamophila, Sowerby. Mega- 

 desma, Bowdich. 



Tijpe, G. reclusa, PI. XXL, Fig. 21. 



Shell very thick, trigonal, wedge-shaped ; epidermis smooth, 

 olive; umbones eroded ; hinge thick, teeth 1.2, laterals indis- 

 tinct ; ligament external, prominent ; pallial sinus distinct. 



Ammal with the mantle open in front ; siphons moderate, 

 with 6 — 8 lines of cilia, orifices fringed ; foot large, compressed ; 

 palpi long, triangular ; gills unequal, united to the base of the 

 siphons, the external pair divided into two nearly equal areas 

 by a longitudinal furrow, indicating their line of attach- 

 ment. 



Distrihition, 6 or 7 species ? Nile, and rivers of West Africa. 



Family XYII. — Solenid^. 



Shell elongated, gaping at the ends ; ligament external ; 

 hinge-teeth usually 2.3, compressed, the posterior bifid. External 

 shell layer with definite cell- structure, consisting of long prisms, 

 very oblique to the surface, and exhibiting nuclei ; inner layer 

 nearly homogeneous. 



Animal with a very large and powerful foot, more or lo^s 

 cylindrical ; siphons short and united (in the typical Solens, with 

 long shells) or longer and partly separate (in the shorter and 

 more compressed genera) ; gills narrow, prolonged into the 

 branchial siphon. 



SoLEN (Aristotle), L. Eazor-fish. 

 Type, S. siliqua, PI. XXIL, Fig. 4. 



