NODULARIA. 137 



A very widely spread form, as \\ill be seen from tlie list of 

 localities quoted above ; to a certain degree it varies considerably ; 

 always corrugatedly sculptured in the umbonal region, this 

 character may be either restricted to the extreme umbone, or 

 spread over the greater portion of the surface of the shell. 



A number of so-called species have been constituted out of its 

 many varietal forms, of which, perhaps, that most often quoted is 

 U. leioiiia, Benson, but on examination of a large series there can 

 be no doubt that these must be relegated to synonym)'. 



Below are given the measurements of four specimens in the 

 Indian Museum, No. 1 being from Calcutta, No. 2 from Bagh, 

 ]Vo. 3 from Umbaila, and No. 4 from Poonassa. 



Long. . . . 

 Lat. . . . 

 Diameter 



Var. gaudichaudi (Et/doiuv). 



Unio f/cmdichaudi, Eydoux, Mag. de Zool, 1838, CI. v, p. 10, 



pi. 118, fig. 3. _ 

 Mar(/aron {Unio) f/atidichauih, Lea, Svn. 1850, p. 32; 1870, 



p.oO. 

 yodularia yandichaiidi, Simpson, Washington, D.C., Smiths. Inst., 



Nat. Mus. Proc. xxii, 1900, p. 812. 



Shell oval, transverse, inequilateral ; umbones not prominent, 

 slightly roughened, covered with a periostracum ; the anterior side 

 is short and rounded ; tlie posterior is broader and obsciu'ely angled ; 

 the whole shell slightly swollen ; texture of shell thin, finely or 

 irregularly striate and covered \Aith a dirty brown or yellowish 

 periostracum ; interior of shell nacreous, of a pinkish violet 

 shade ; hinge very narrow and nearly straight, a single, rough and 

 projecting cardinal tooth appearing on the right valve and two 

 oblique and unequal cardinal teeth in the left \alve; lateral teetli 

 very thin, smooth, obliquely truncate at the posterior end, the 

 plates of the opposite valve, between which it fits, of nearly equal 

 size. 



Long. 22-5, lat. 38-25 mm. 



Hah. Kivers of Bengal. 



Var. keraudreni {E)jdou,v). 



Unio keraudreni, Evdoux, Mag. de Zool. 1838, CI. v, p. 8, pi. 118, 



fig. 1. 

 yiuryaron ( Unio) keraudreni, Lea, Syn. 1852, p. 30 ; 1870, p. 46. 



Shell oblong-oval e, somewhat depressed, very inequilateral, 

 smooth ; anterior side obtuse, short ; posterior side gently 

 attenuated with blunt extremity ; umbones scarcely prominent, 

 much eroded ; remainder of outer surface covered with a dark 

 brown periostracum ; interior of shell nacreous and tinged with 



