1866. ] Contributions to Indian Malacology. 139 
Lam. It differs totally from all the shells referred to that species, 
and all its numerous varieties are easily distinguished both from 
Lamarck’s and Chemnitz’s types of corrugatus. U. favidens is more 
inequilateral, it is a thicker shell with much stronger and broader 
cardinal teeth. The type, too, is more angulate, both anteriorly and 
posteriorly. The following varieties of U. favidens, with their 
localities, are described by Mr. Benson in the Ann. and Mag. Nat, 
Hist. Vol. X, pp. 188, 189. 
Unio favidens, type. Bhitoura on the Ganges between Cawnpore 
and Allahabad. 
vor. marcens,......... Burhampooter river, Assam. 
Me EURUGON Gs ues een. Nujeebabad in the north-west of Rohilkund. 
3 IDO: Aono . Jellinghy river, Bengal. 
A ,, Chrysis, .........Dojora river, Kareily Ghat near Bareilly. 
5 5 ROCKO, cobcoosor “ Jheel” between Humeerpore and Someer- 
pore, Bundelkund. 
GREE CENSOR Bese ceee ness Ganges river above Chunar. 
No. 6.—Unio Camrutevus, Lea.—Hoogly river, 100 miles above 
Calcutta. 
Lea, Trans. Am. Phil. Soc. IV, 95, Pl. 13, f. 25. 
Benson, J. A. S. B. IV. 450. 
Kiister, Mart. and Chem. p. 228, Pl. 77, fig. 4. 
The two figures agree perfectly. The type is a very thin shell, 
with fine lamellar teeth. Specimens exist in the Asiatic Society’s 
Museum, brought from Bhagulpoor. The form is widely distributed 
in N. India; I have even a variety from Sind. 
No. 7.—Unto sinmveatus, Lea. Hoogly river with the last. 
Symphonota bilineata, Lea, Trans. Am. Phil. Soc., IV. 98, pl. 11, f. 19. 
ah Benson, J. A. 8. B. IV. 452. 
Benson, (Ann. Mag. Nat. Hist. Ser. 3, Vol. X., pp. 187, 195) shews 
that this is merely the very young form of U. marginalis, Lam. He 
is unquestionably correct. The ‘‘ two delicate lines passing from the 
beaks to the posterior region” are, like many other umbonal mark- 
ings, characteristic of young shells, and disappear gradually with age. 
The remains of them, much blunted, are oiten to be detected on 
adults, 
