AVICULID^. 2'75 



byssal opening anterior to the beaks ; anterior wing wanting, 

 posterior wing large. 



Ambonychia, Hall, 1843. 



Syn. — Pimopsis, Hall, 1843. 



I)i)<tr. — 15 sp. Lower Silurian — Carboniferous ; United States, 

 Europe, Australia. A. bellistriata^ Hall (cxxx, 49). 



Roundly snbquadrangular, equivalve, moderately inflated, 

 with anterior incurved beaks and a posteriorly extended 

 straight hinge-line, anterior side straight, below the beaks 

 slightl}^ 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, 1813. (Megaptera, M. and W,, 1866 

 [not Gray]. Opisthoptera, Meek.) Subtrigonal, subequivalve, 

 posteriorly with a very large pointed wing, obtusely convexlj'- 

 angular from the beak to the inferior narrow end, beaks anterior, 

 terminal, incurA'ed, 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). 



Amphiccelia, Hall, 1861. 



Distr. — 3 sp. Palaeozoic; U. S. A. Leidyi, Hall (cxxx, 33). 



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. 



LuNULACARDiuM, Munstcr, 1846 (Zittel, 1881). 



Distr. — Devonian ; Eur. L. semistriatum, Miinst. 



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, Chaenocardia, Meek 

 and Worthen. 



GossELETiA, Barrois, 1881. 



Distr. — G. Devonica, Barrois. Devonian ; Spain. 



Shell equivalve, inequilateral, gibbous, oblique, posteriorly 



