146 VNIONIIHE. 



281. Nodularia (Nodularia) involuta (Benson). 



Nodularia (Nodularia) involuta (Benson) ; Simpson, Washington, 

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



Unio involutus (Benson), in Hanley, Rec. Biv. Shells, 1856, p. 385, 

 pi. 23, fig. 19 j H. & T., C. I. p. 19, pi. 41, tig. 2. 



Original description : Peaked ovate, not so very inequilateral, 

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

 rather pale green, very obscurely subradiated ventrally with ochre- 

 yellow, rather tinged with blue dor sally, 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 uinbonai 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 mm. 



Hob. 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 EADIATULA. 



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

 Proc. xxii, 1900, p. 820. 



TYPE, Unio crispisulcatus, Benson ; Burma. 



Range. Burma ; Assam ; Cambodia. 



Original description'. Shell rather solid, triangular oval, with 

 high beaks which are but little 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 leg's into nodules or cancellations by concentric 

 sulcations; the sculpture of the posterior slope stronger, and 

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

 the anterior 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, D.O., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, p. 820. 



