NODULARIA. 137 



A very widely spread form, as will be seen from the 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. leioma, Benson, but on examination of a large series there can 

 be no doubt that these must be relegated to synonymy. 



Below are given the measurements of four specimens in the 

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

 No. 3 from Umballa, and No. 4 from Poonassa. 



1. 2. 3. 4. 



Long 20 17-25 25-25 30mm. 



Lat 39-75 30 49-5 56 mm. 



Diameter 12 11 18-75 21 mm. 



Var. gaudichaudi (Eydoux). 



Unio gaudichaudi, Eydoux, Mag. de Zool. 1838, Cl. v, p. 10, 



pi. 118, fig. 3. 

 Margaron (Unio) gaudichaudi, Lea, Syii. 1850, p. 32; 1870, 



p. 50. 

 Nodularia gaudichaudi, 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 ; the posterior is broader and obscurely angled ; 

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

 irregularly striate and covered with 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 valve; lateral teeth 

 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. 



Hob. Rivers of Bengal. 



Var. keraudreni (Eydoux). 



Unio keraudreni, Eydoux, Mag. de Zool. 1838, Cl. v, p. 8, pi. 118, 



fig. 1. 

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



Shell oblong-ovate, 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 



