200 GLAUCOMYIl)-^. 



Suborder CONCH ACE A. 



Family GLAUCOMYID^. 



Subfamily GLAUCOMYIN^. 



Shell transversely elongate, thin, covered with a periostraciiui ; 

 hiuge bearing three cardinal teeth in each valve : lateral teeth 

 absent ; ligament external, elongated; pallial line sinuons. 



Animal inhabiting either fresh or brackish water; siphons very 

 long, united ; gills nnequal, the external the smaller and appendi- 

 culate ; foot small. 



Distribution. India ; China ; Malaysia. 



Genus TANYSIPHON. 



Tanysij}?wn, Benson, A. M. N. II. ser. o, i, 1858, p. 40s, pi. 12. 

 Type, Tani/sijJion rivulis, Benson, from Bengal. 



Range. Gangetic Delta. 



Original description : — " Testa subiniequivalvis, inaequilateralis, 

 transverse oblonga, umbonibus promineutibus obtiisis, extremi- 

 tatibus (postica maxiine) hiautibus, margine superioi'i subarcuato, 

 veutrali subrecto. Cicatrix siplioiialis elongata -^']j longitudinis 

 testa? invadens. Yah*a3 dextrae dentes tres, 1 anterior angustiis 

 promineus intrans, 2 laminares transversi, medianus prominens, 

 posterior major obtusus ; valvtc sinistrae dentes duo, anterior 

 bilobatns, posterior major. Ligamentum duplex, externum 

 parvum ellipticuni, vix convexiusculum, internum lineare foveam 

 posteriorem occupans, demum lamiuam cardinalem perpendi- 

 culariter truncans. Epidermis tenuis. Area interior test» nitida, 

 non margaritacea. 



Some of the teeth are apt, in large specimens, to become 

 obsolete. 



Benson makes the following remarks on the animal: — 



•• The siphons closely resemble those organs \u Mya truncata, 

 Linn., AVoodward, p. 317, fig. -?20. Both are united in a finely 

 annulated compressed scabbaj-d nearly equalling the length of the 

 shell. A raphe or seam appears along the inferior margin of the 

 scabbard. Tiie free extremity is surrounded by tentacula, which 

 are distant, and of unequal length. The orifices of the siphons 

 are papillar ; that of the branchial siphon, the larger, is provided 

 with minute tentacnla, but the oriGce of the exhalant siphon is 

 naked. The small foot is hatchet-shaped, with the posterior 

 margin notched. Both the siphons and the foot are wholly 

 retractile, and highly sensitive. The foot is sometimes extended 

 and tongue-shaped, but generally of the outline represented." 



