146 UNIOA'ID^, 



281. Nodularia (Nodularia) involuta (Benson). 



Nodnlaria {Nodularia) involuta (Benson) ; Simpson, Wasliington, 

 D.C., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, p. 817. 



Unio involulus (Benson), in Hanley, Bee. Biv. Shells, 1856, p. 385, 

 pi. 23, fig. 19 ; n. & T., C. I. p. 19, pi. -11, fig. 2. 



Original descri/ption : — Peaked ovate, not so vei\y inequilateral, 

 compressed in front, swollen in the umbonal region, thin, polished, 

 rather pale green, verj obscurely subradiated ventrally with ochre- 

 yellow, rather tinged with blue dorsally, marked with 2 or 3 dark 

 green lines on the anterior slope, partially marked with some 

 close and regular shallow groove-like posterior wrinkles, elsewhere 

 smooth ; ventral edge strongly arcuated and much rising behind, 

 less curved yet almost equally rising in front ; anterior side 

 tapering to a blunt subcentral peak, no umbonal ridge ; hinder 

 dorsal edge nearly straight, scarcely sloping ; umbones swollen, 

 prominent, with a few longitudinal corrugations ; beaks incurved ; 

 nacre silvery ; umbonal cavity ample ; lateral teeth large, laminar, 

 raised, the shorter one very elevated at its extremity. 



"In the single specimen described from, there is no cardinal 

 tooth, but the hinge-plate is elevated beneath the umbones." 



Long. 34, lat. 48 nun. 



Hah. Assam. 



A curiously thin, smooth, boat-shaped form which is consider- 

 ably inflated, the diameter respectively of a right and left valve 

 in the British Musum Collection being 10-75 and 9-5 mm. 



Section BADIATULA. 



Jtadiatula, Simpson, Washington D.C., Smiths. Inst., Nat. Mus. 

 Proc. xxii, 1900, p. 820. 



Type, Unio crisinsuhatus, Benson ; Burma. 



Range. Burma ; Assam ; Cambodia. 



Original description: — Shell rather solid, triangular oval, with 

 high beaks which are but httle inflated, not very full at post base, 

 bluntly pointed behind, the beaks and entire surface covered with 

 radiating, occasionally slightly zigzag or divaricate ridges, which 

 are cut more or less into nodules or cancellations by concentric 

 sulcations ; the sculpture of the posterior slope stronger, and 

 curving upward ; pseudocardinals of the left vahe 2 to 3, ragged, 

 the antex'ior larger, two in the right valve, with a parallel-sided 

 socket, the larger teeth compressed but rather solid. 



282. Nodularia (Radiatula) crispisulcata (Benson). 



Nodularia (Radiatula) crispisulcata (Benson) ; Simpson, Wash- 

 ington, B.C., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, p. 820. 



