PARRliVSIA I 107 



(Inio fitlminens Philippi, Conch., HI, 1847, P- 4^, pi. m, tigs. 



5, 6. — KusTER, Conch. Cab. Unio., 1862, p. 286, pi. xcvi, 



figs. 2, 3. 

 Unio liitens Lka, Pr. Ac. Nat. Sci. Phila., VIII, 1856, p. 93. 

 Unio iuteus Lka, Jl. Ac. N. Sci. Phila., Ill, 1857, p. 291, pi. 



XXIV, fig. 4; Obs., VI, 1857, p. II, pi. XXIV, fig. 4. 

 Mar gar on (Unio) Iuteus Lea, Syn., 1870, p. 46. 

 f Unio semirugatus Ci-ienu, 111. Conch., 1858, pi. xii, figs. 2, 2a. 

 Unio merodabensis Kuster, Conch. Cab. Unio, 1861, p. 233, 



pi. EXXVIII, fig. 4. 

 Unio zvynegungccnsis PIanley and TniiOBALD, Conch. Ind., 



1876, p. 21, pi. XLV, fig. 6. 

 Unio tennenti Hanlky and Theobald, Conch. Ind.. 1876, p. 



22, pi. xhv, figs. 7-9. 

 Unio phayresi Theobald, manuscript. 



The shells of this group are very variable and, it seems to 

 me, have received far too many names at the hands of conch- 

 ologists. I have given as varieties some of these and others 

 have not seemed to me to be worthy even of that rank. 



Miiller's description of Mya corrttgata is inadequate, but in 

 the Beschaftigungen it is further discussed and characteristic 

 figures are given of the species we know as Unio corntgatiis 

 of India. 



The form that I take to be typical, and my views in this 

 matter agree with those of Hanley and Theobald, is of mod- 

 erate size, narrowed a little in front, rather full behind the 

 middle of the base, rather smooth and shining. The beak 

 sculpture consists of strong, radial ribs, which extend out on 

 to the disk and are zigzagged below. Sometimes the beak 

 sculpture is but slightly developed or absent in specimens, 

 which seem to be typical in other respects. 



Var. lce-7'irostris (Benson). 



According to the figures of Hanley and Theobald, this form 

 is more elongated than the type, has quite full beaks, which 

 may be strongly sculptured, and is not inflated behind the mid- 

 dle of the base. It appears to merge into the typical form.. 

 Unio Icez'irostris Benson. Ann. and Mag.. 1862, p. 192. 



