20 
CONCHOLO GIA INDICA. 
PLATE XL III. 
UNIO. 
1. U. Thwaitesii, Lea, Proc. Pliilad. Ac. N.S. vol. 1 
(1859), p. 152 ; J. Pliilad. s. 2, vol. 4, pi. 37, 
f. 125.— Peeve, Conch. Icon. Unio, f. 105. 
Ceylon. 
XI. marginalis, Lamarck, Anim. s. Vert. ed. Desh. 
vol. 6, p. 544. — Hanley, Rec. Bivalves, p. 206, pi. 
19, f. 53. — IT. testudinarius, Spengler, Skriv. Nat. 
Selks. vol. 3, pt. 1, p. 65, and U. truncatus, p. 56 
(fide Morch). — U. Gramlandicus (in Lea) from 
Schroter, Fluss. Conch, p. 181, pi. 9, f. 1. 
We describe the hinge of the typical form, which is 
but little modified in any of the varieties. In the right 
valve are two sloping anterior teeth, of which the 
upper and narrower arches more or less downwards, 
and the lower is strong and rather large; the single 
lateral one is strong, elongated, and bent at the end. 
In the left valve, besides the callus, there is one ante- 
rior and two lateral teeth, the latter scarcely divided 
until the second moiety, where they slant down. The 
principal anterior scar is decidedly large in proportion 
to its size in the allied species. After long examina- 
tion of many scores of 1 examples of this most variable 
species from nearly every part of British India, we can 
only arrive at the conclusion that the forms usually 
designated in cabinets, bilineatus, lamellatus, Corrianus, 
&c., all run into each other. We do not assert, how- 
ever, that the shells intended by Lea are identical ; for 
his figure of bilineatus looks like the young of some 
broadly- winged Siamese shell (of the Housei type), and 
his lamellatus is notable for a peculiarity of dentition. 
We have delineated some of the more striking forms. 
2. XT. marginalis, var. typica. — U. marginalis, En- 
cycl. Meth. Vers, pi. 247, f. 1. 
Moradabad : Pegu. 
The brief Lamarckian diagnosis is further defined 
by his reference, &c., and his figure. 
3. XT. marginalis, var. obesa. 
River Irawadi, Birmah. 
A giant form, which does not exhibit the ochraceous 
band, and is peculiarly swollen. It comes between the 
var. lata, and the typical form. The upper anterior 
tooth is almost linear ; the lateral are not bent at the 
extremity, and the tipper one in the left valve is 
sscarcely developed. 
4. XT. marginalis, var. Candaharica, Hutton, J. 
Asi. Soc- Beng. vol. 17, pt. 1 (1849), p. 651. 
River Sutlej. 
The abnormal characters of shape and colouring are 
such that Hutton (its discoverer) suggested its possible 
distinctiveness. The nucleus very closely approaches 
U. theca, Benson ; the adult cannot be separated from 
the form bilineatus. 
5. XT. marginalis, var. tricolor. — U. tricolor, Kuster. 
ed. Chemn. Unio, pi. 45, f . 1 ? 
A very beautifully painted shell, which is usually 
more or less compressed. 
PLATE XLIV. 
UNIO. 
1. U. marginalis, var. cylindrica. 
2. U. marginalis, var. zonata. — U. marginalis, Desh. 
Encycl. Metli. Vers, vol. 2, p. 587. 
Belgaum, Deccan. 
3. U. marginalis, var. bilineata. — U. bilineatus, 
Reeve (as of Lea), Conch. Icon. Unio, f. 365. 
Nearly all the varieties (especially the immature 
examples) exhibit two raised lines near the beaks on the 
umbonal slope. We are aware that Spengler intended 
to have indicated U. marginalis as U. testudinarius, 
but his Latin description is most utterly inadequate to 
define it ; his delphinus, conus, and gibbosus (from the 
East Indies), must be ignored for a similar reason. 
The name Grsenlandicus (the locality was subsequently 
corrected in the Einleitung, vol. 2, p. 621, by Schroter 
himself), would mislead. 
4. U. marginalis, var. Corriana. — U. Corrianus, Lea, 
Trans. Amer. Phil. Soc. vol. 5, p. 177, pi. 9, f. 25, 
from which Hanley, Rec. Bivalves, p. 207, pi. 21, 
f. 60. 
Near Calcutta, &c. 
This form, always more or less indented in the middle, 
is sometimes elongated cylindrical, sometimes com- 
pressed and oval-oblong. The cardinal callosity (rarely 
absent) is more or less developed, and the anterior or 
hinge teeth are almost horizontal, curve outward, and 
are either rather elongated, or if shorter, are rather 
prominently elevated. 
