Species of the Genus Unio. 187 



giorie; dentibus cardinalibus laminatis, tenuibus, brevibus, utriusque 

 valvae duplicibus, valvse dextrse prope marginem anteriorem sitis, 

 obliquis ; sinistra? lobo subapicali transverso, anteriore obliquo, la- 

 teralibvis elongatis, vix curvatis, valva? dextrse simplicibus, sinistrae 

 duplicibus : margarita lutea, versus marginem ventralem albida. 



Long. 20, lat. 40, diam. 10 mill. 



Habitat in fluvio Cane, prope Banda, Bundelkhund. 



Interior of shell transversely subplicate ; cavity of beaks shal- 

 low. Anterior cicatrices separate, posterior confluent, apical 

 ones in the cavity of the beaks. Some slight ruga? are visible 

 on the posterior slope at right angles to the stria? of growth. 



This shell, of which I found a single specimen, belongs to the 

 Corrianus type of Unio marginalis, and is remarkable for its 

 elongate-ovate non-rhomboidal form. Unio marginalis, although 

 so abundant in other parts of the north-west, and occurring also 

 in the upper part of the river Jumna, near Delhi, never was 

 captured by me, in the branch of that river where I discovered 

 this species, before 1830, and it has not appeared in any other 

 collection made in the Gangetic region. The shell is somewhat 

 wider posteriorly than anteriorly. The pale opake straw-colour 

 of the unpolished epidermis is also a peculiar feature, not ob- 

 servable in any other Northern Indian species. 



As in U. bilineatus, Lea, which occurs everywhere with U. 

 marginalis, and which appears to me to be the young of that 

 species, varying according to its varieties, the double umbonal 

 line, apparent occasionally in adult specimens of U. marginalis, 

 is conspicuous. 



4. Unio macilentus, B., n. sp. 



U. testa transverse rhomboideo-subovata, valde insequilaterali, tenui- 

 uscula, compressiuscula, antice rotundata, postice alata, recta, turn 

 descendente, demum obtusa, margine ventrali convexiusculo ; disco 

 striato, medio radiato-rugoso, versus marginem transverse plicato; 

 epidermide fuscata, versus marginem ventralem viridescente ; urn- 

 bonibus convexiusculis undato-sulcatis, decorticatis, ferrugineis, 

 apice prominulo ; ligamento elongato ; linea umbonali convexius- 

 cula ; ala planiuscula, radiato-sulcata ; dentibus cardinalibus bre- 

 vibus, subverticalibus, duplicibus, erosis, lateralibus longiusculis 

 rectis, valva? sinistra? duplicibus : margarita versus marginem iri- 

 descente, versus apicem colore salmonis tincta. 



Long. 24, lat. 42, diam. 15 mill. 



Habitat in rivulo Choia Nuddy dicto, non procul a Bijnore, provincise 

 Rohilkhund. 



Anterior cicatrices separate, posterior confluent, apical in a 

 row in the angle at the base of the cardinal tooth, the inner 

 lobe of which in the right and the outer in the left valve are erect. 



I took a single specimen of this shell in a hurried search at 



