CONCHOLOGIA INDICA. 



19 



PLATE XLI. 

 UNIO. 



See previous plates, ix. to xii. 



1. IT. Layardi, Lea, Proc. Ac. Nat. Sc. Philadelph. 

 1859, p. 153 : Journ. Ac. Nat. Sc. Philad. ser. 2, 

 vol. 4 (and Obser. U. vol. 7), pi. 36, f. 122.— 

 Eeeve, Conch. Icon. Unio, f. 111. 



Cejlon. 



We are unable to distinguish the exact line of de- 

 marcation between this and Thwaitesii; in charac- 

 teristic specimens, however, the front extremity is 

 longer and more tapering. 



2. IT. involutus, Benson, in Hanley's Recent Bi- 

 valves, p. 385, pi. 23, f. 19. — Keeve, Conch. Icon. 

 Unio, f. 177. 



Assam. 



3. TJ. favidens, var. chi-ysis, Benson, Ann. Nat. 

 Hist. ser. 3, vol. 10 (18G2j, p. 188. 



River Dojora at Kareily Ghat, near Bareilly. 



4. TJ. Jenkinsianus, Benson, An. Nat. Hist. ser. 3, 

 vol. 10 (18G2), p. 185. 



River Berhampooter, Assam. 



The unique type here figured will probably be con- 

 sidered an abnormal form of marginalis or Corrianus. 



5. 6. U. Nuttallianus, Lea, Journ. Ac. Nat. Sc. 

 Philad. ser. 2, vol. 3, p. 310, pi. 30, f. 25 : Obser. 

 U. vol. 6, p. 30, pi. 30, f. 25. 



Assam. 



7. XT. eonsobrinus, Lea, Journ. Ac. Nat. Sc. Philad. 



ser. 2, vol. 4 (and Obser. U. vol. 7), pi. 90, f 192. 



— Benson, An. Nat. Hist. ser. 3, vol. 10 (1862), 



p. 195. 



Cochin, Malabar. 

 Only two specimens, both in the Bensonian collec- 

 tion, are known to us. They approach marginalis, of 

 which they may possibly prove a tumid variety, yet 

 have a fibrous, not a satin-like, style of epidermis, a 

 different shape, and a different disposition of colouring, 

 the yellow band not being adjacent to the ventral edge. 

 There is no appearance, moreover, of the two raised 

 lines which adorn the umbonal slope near the beaks, 

 which, unfortunately being eroded, do not exhibit any 

 marked character. The front extremity is more pro- 

 minent and rounded (not obliquely cut off below) than 

 in the allied forms. According to Lea the original 

 types came from China. 



PLATE XLII. 

 UNIO. 



1. U. Birmanus, Blanford, Proc. Zool. Soc. 1869, 

 p. 450. 



Bhamo, Upper Birmali. 



2. U. favidens, var. Delta, Benson, An. Nat. Hist, 

 ser. 3, vol. 10 (1862), p. 188. 



River Jellinghy, Upper Gangetic Delta, Ben- 

 gal. 



The radiation spoken of consists of almost imper- 

 ceptible lines. A specimen from Tirhoot is of an 

 uniform dark olivaceous hue. 



3. U. foliaceus, Gould, Proc. Boston Soc. N. II. 

 vol. 1, p. 141 : Otia Conch, p. 191. — U. Pegueusis, 

 Anthony, American J. of Conch, vol. 1 (1865), 

 p. 351, pi. 25, f. 2. — Reeve, Conch. Icon. Unio, 

 f. 519. 



Tavoy, Birmah ; Pegu. 



Gould's type (sent to Benson), is unmistakably the 

 young of the adult Peguensis. 



4. 5, 6. marcens, Hanley, for U. favidens, var. mar- 

 cens of Benson, An. Nat. Hist. ser. 3, vol. 10 (1862),- 

 p. 188. 



Berhampooter River, Assam. 



The absence of all corrugation is a most important 

 characteristic feature. 



7. U. marginalis, var. Anodontina. — U. Anodon- 

 tinus, Kuster (not Lamarck), ed. Chemn. Conch. 

 Unio, pi. 80, f. 5. 



River Godavery ; Nagpoor ; Sylhet. 



Although we have not fully traced the intervening 

 links between this elongated form and the typical mar- 

 ginalis, we cannot doubt its approximation to those 

 specimens which have been supposed (perhaps erro- 

 neously) to represent the U. bilineatus of Lea. Vir- 

 ginia is the recorded, and probably the correct, locality 

 of the Lamarckian U. Amodontoides, but the types are 

 declared to be Indian, not American ; its dentition is 

 said to be inconspicuous. In the specimen delineated 

 the front teeth are short, strong, and very oblique ; the 

 nacre is of a rather pale salmon-colour. 



