TRIBE MAILLEACEA. 261 
linear, usually much distorted, straight or curved, flattened, fra- 
gile: white, tinged with reddish violet, margins of the sides sub- 
parallel, base retuse, slightly winged on one side, obsoletely mu- 
cronated. 3. Timor and Nicobar Isles. Allied to the last. 
M. Decurratus. Lam. 6.—Del. t. 14. f. 6. Small, oval or 
oblong, flattened, fragile; base variable, ligamental pit very short. 
—Australia. 
AVICULA. 
Shell inequivalve, fragile, not externally foliaceous, with the dorsal 
margin straight, transverse, and produced at both extremities, the 
anterior of which is caudiform ; valves oblique, the left one emar 
ginate, with a sinus or notch, through which the byssus passes ; 
hinge linear, with one tooth on each valve under the beaks ; liga- 
ment linear and marginal, placed in a long narrow groove, not 
traversed by the byssus. 
A. Macroprera. Lam.—Mytitus Hrrunpvo var. D. Gimel. 
—Gualt. t. 94. A—Kn. 6. t. 2. Very large, blackish brown (when 
very young, with whitish rays) ; wing very ample, obliquely curved, 
tail rather long and almost linear at its termination, body extremely 
elongated, within pearly, becoming reddish by age.—Var. A 
Lotorium. Lam. 2.—With the tail very short. 7.—W. Indies. 
A. Semisacirta. Lam. 3.—List. t. 220. f. 55.—Kn. 4. ft. 8. 
f. 5.. A Macroprera Jun. Bl. t. 63. f. 3. Black or reddish 
yellow, body short and very oblique; the ears oblique, equal, pro- 
minent, subventricose, the tail long.—Var. Reddish yellow, obso- 
letely rayed with brown.— Australia.— Africa ? 
A. Hererorrera. Lam. 4.—Del.t. 14. f. 7. Yellowish or 
reddish, transversely elongated, the posterior lobe having the shape 
of a spear point and very oblique; one valve anteriorly shorter 
than the other: tail elongated.—Var. Blackish with the wing 
less oblique.—Red Sea? 
A. Crocea. Lam. 6.—Glabrous, uniform orange yellow, pos- 
terior appendage obliquely diverging. Var, A. Rump. t. 46. G? 
Rich orange, the hinge margin extremely elongated so that the tail 
is long and acute, the body being short and narrow: posterior ap- 
pendage rather large, the sinus nearly rectangular. Var. B. Tail 
short, not longer than the posterior wing. Var. C. Avicua 
Cuinensis. Leach. Z. M. 2. t. 114. Citron yellow, the tail 
short.—Isle of France. (for A and B.) ! 

1M. Deshayes states that the Fatcara of Lam. 5, is the same 
species as Tarentina. 
