200 GLAUCOMYID^;. 



Suborder CONCHACEA. 



Family GLAUCOMYID^. 



Subfamily GLAUCOMYINJE. 



Shell transversely eloDgate, thin, covered with a periostracuin ; 

 hinge bearing three cardinal teeth in each valve ; lateral teeth 

 absent ; ligament external, elongated; pallial line sinuous. 



Animal inhabiting either fresh or brackish water ; siphons very 

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

 culate ; foot small. 



Distribution. India ; China ; Malaysia. 



Genus TANYSIPHON. 



Tanysiphon, Benson, A. M. N. H. ser. 3, i, 1858, p. 408, pi. 12. 

 TYPE, Tanysiplion rivalis, Benson, from Bengal. 



Range. Gangetic Delta. 



Original description : " Testa subincequivalvis, iuaBquilateralis, 

 transverse oblonga, umbonibus prominentibus obtusis, extremi- 

 tatibus (postica maxime) hiantibus, margine superiori subarcuato, 

 ventrali subrecto. Cicatrix siphonalis elongata ^ longitudinis 

 testa? invadens. Valvse dextra dentes tres, 1 anterior angustus 

 prominens intrans, 2 laminares transversi, medianus prominens, 

 posterior major obtusus ; valvre sinistra3 dentes duo, anterior 

 bilobatus, posterior major. Ligamentuni duplex, externum 

 parvum ellipticum, vix convexiusculum, internurn lineare t'oveam 

 posteriorem occupans, demum laminam 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 in My a truncata, 

 Linn., Woodward, *p. 317, fig. 220. Both are united in a finely 

 annulated compressed scabbard nearly equalling the length of the 

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

 scabbard. The 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 tentacula, but the orifice 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." 



