AVICULIDA. 275 
byssal opening anterior to the beaks; anterior wing wanting, 
posterior wing large. 
AmBonycuHiA, Hall, 1843. 
Syn.—Pimopsis, Hall, 1843. 
Distr.—15 sp. Lower Silurian—Carboniferous; United States, 
Europe, Australia. A. bellistriata, Hall (exxx, 49). 
Roundly subquadrangular, equivalve, moderately inflated, 
with anterior incurved beaks and a _ posteriorly extended 
straight hinge-line, anterior side straight, below the beaks 
slightly insinuated and gaping, posterior truncate ; hinge 
anteriorly below the beaks with a few short oblique, and pos- 
teriorly towards the termination of the hinge-line, also with a 
few subparallel or slightly diverging rib-like teeth; posterior 
muscular scar large, subcentral, anterior very small or nearly 
obsolete. 
ANOMALODONTA, Miller, 1873. (Megaptera, M. and W., 1866 
[not Gray]. Opisthoptera, Meek.) Subtrigonal, subequivalve, 
posteriorly with a very large pointed wing, obtusely convexly 
angular from the beak to the inferior narrow end, beaks anterior, 
terminal, incurved, slightly projecting above the hinge-line, 
anterior wing probably obsolete ; hinge with a few small anterior 
teeth below the beak, as in Ambonychia; posterior muscular 
scar large, subcentral, pallial line extending anteriorly up to 
very near the beak. This form is considered by its authors to 
be a subgenus of Ambonychia, differing from it by the very 
strong development of the posterior wing, on which no internal 
ribs have as yet been observed. A. Casei, M.and W. (cxxx, 50). 
Ampuicaita, Hall, 1867. 
Disir.—3 sp. Paleozoic; U.S. A. Leidyi, Hall (exxx, 38). 
Shell (cast) subrhomboidal, with elevated beaks, beneath which 
appears a large triangular cartilage-pit, and a second smaller pit 
anterior to it; no teeth have been discovered on the extension 
of the hinge-line; muscular impressions faint, shell thin. 
LunuLacarpium, Munster, 1846 (Zittel, 1881). 
Distr.—Devonian; Eur. JL. semistriatum, Munst. 
Shell obliquely oval, like Lima, radially sculptured; with a 
straight, toothless hinge ; posteriorly shortly winged ; anteriorly 
excavated, with a deep lunule and narrow byssal opening. 
A portion of the species originally referred to this group, 
appears similar to, perhaps identical with, Chenocardia, Meek 
and Worthen. 
GossELETIA, Barrois, 1881. 
Distr.—G. Devonica, Barrois. Devonian; Spain. 
Shell equivalve, inequilateral, gibbous, oblique, posteriorly 
