24 Dr. J. E. Gray on some Families of Bivalve Shells. 



4. Pharella. Siphons shortly produced, separate ; umbo sub- 

 anterior ; anterior adductor muscle elongate, subtrigonal ; shell 

 subcylindrical. P.javanica, P. Michaudi, P. acutidens. 



5. Pharus. Siphons produced, separate; shell compressed ; 

 umbo subcentral ; anterior adductor muscle elongate, horizontal ; 

 umbonal ribs rudimentary. P. legumen. 



6. Cultellus. Siphons ? anterior adductor muscle 



rounded, hinder triangular; shell compressed; umbo subanterior. 

 C. lacteus. 



b. Sijjhons much produced, large, united, covered with a thick 



periostraca ; retractor siphonal muscles small; siphonal in- 

 flection very small. 



7. Cyrtodaria. Anterior adductor muscle elongate ; umbo sub- 

 posterior. C. glycimeris. 



c. Siphons elongate, with large fan-shaped retractor muscles ; 



siphonal inflection deep, rounded. 



* Siphons very large, united, covered with a hard periostraca. 

 Shell compressed. Hinge-teeth 3 ■ 3, compressed. 



8. Siliqua. 



** Siphons large, united at the base, covered ivith a hard perios- 

 traca. Shell subcylindrical. Hinder teeth conic. 



9. Glycimeris. 10. Adacna. 



*** Siphons very large, united at the base, upper part free, ringed. 



11. Macha. Shell obliquely sulcated. M. strigillatus. 



12. Azor. Shell smooth. A. antiquatus. 



**** Siphons elongated, cylindrical. 



13. Tagelus. * Umbo submedial; siphonal inflection very 

 deep, beyond the umbo. T. viridiceneus. T. Carabceus. 



** Novaculina. Umbo subposterior ; siphonal inflection deep, 

 not reaching the umbo. T. Novaculina, India. T. Dombei, 

 Peru. T.fragilis, Europe. T. constrictus, China. 



Elisia. — Animal unknown. Shell suborbicular, oblong, equi- 

 valved, compressed, thin, covered with a hard shining periostraca; 

 umbo not prominent, subanterior. Cardinal teeth oblique, in 

 right valve two, hinder bifid elongate, in left valve three, central 

 bifid. Pallial impression submarginal. Siphonal inflection deep, 

 oblong, rather contracted at the outer edge, descending from the 

 upper part of the hinder margin to the centre of the disk. 



Elizia orbicu/ata = Solen orbiculatus, Gray in Wood Cat. Sup- 

 plement, t. 1. f. 4. 



