462 



LAMELLIBRANCHIA TA. 



[ANG. ANT. 



FIG. 774. Angellura 

 cuneatum. 



ANGELLUM, S. A. Miller, 1878, Jour. Gin. 

 Soc. Nat. Hist., vol. 1, p. 105. [Ety. 

 aggos, a pail; ellus, 

 diminutive.] Equi- 

 valve, hanging 

 down; um bones 

 prominent ; beaks 

 incurved, winged 

 posteriorly ; c o n - 

 centrically lined. 

 Type A. cuneatum. 

 cuneatum, S. A. Mil- 

 ler, 1878, Jour. Gin. 

 Soc. Nat. Hist. vol. 

 1, p. 106, Hud. 

 Riv. Gr. 



ANODONTOPSIS, McCoy, 1851, Ann. and Mag. 

 Nat. Hist., 2d series, vol. 7, p. 54. [Ety. 

 from the resemblance to the shells of 

 the genus Anodonta.] Equivalve, ine- 

 quilateral, compressed; rotundato- 

 quadrate or subtrigonal ; posterior side 

 wide, round, or obliquely subtruncate ; 

 anterior end slightly contracted in front 

 of the beak ; beaks small, prominent 

 nearer the anterior than posterior end ; 

 hinge-line shorter than the length of 

 the shell, with a posterior long, slender, 

 lateral tooth extending just below it 

 (double in the right valve), and another 

 similar but shorter one in front of the 

 beaks ; anterior and posterior muscular 

 impressions ovate ; slight clavicular ridge 

 between the beak and the adductor im- 

 pressions ; pallial impression entire ; 

 surface smooth or concentrically lined. 

 Type A. angustifrons. Part of the gen- 

 eric definition is from A. milleri, as the 

 interior of the type is not known, 

 amygdaliformis, Walcott, 1885, Monogr. 

 TJ. S. Geo. Sur., vol. 8, p. 180, Devonian. 

 oncinna, Whiteaves, 1884, Pal. Foss., vol. 

 3, p. 12, Guelph Gr. 



ridge to the termination of the poste- 

 rior wing, and also from the cardinal 



FIG. 775. Anodoutopsis milleri. 



(?) milleri, Meek, 1871, Am. Jour. Sci., 3d 

 series, vol. 2, p. 297, and Ohio Pal., vol. 



1, p. 140, Hud. Riv. Gr. 

 unionoidea, see Modiolopsis unionoides. 

 ventricosa, Billings, 1874, Pal. Foss., vol. 



2, p. 55, Gaspe limestone No. 8, Devo- 

 nian. 



ANOMALODONTA, S. A. Miller, 1874. Gin. 

 Quar. Jour. Sci., vol. 1, p. 16. [Ety. 

 anomalos, irregular; odous, tooth.] Equi- 

 valve, inequilateral, alate posteriorly, 

 abrupt anteriorly ; umbones high ; 

 beak incurved ; deeply sinuate for the 

 bysaus; cardinal ridge beneath the 

 umbone sloping posteriorly; cartilage 

 grooves extending from the cardinal 



FIG. 776. Anomalodonta gigantea. 

 Hinge-line of right valve. 



ridge to the byssal sinus; 

 nnterior muscular scar be- 

 low the byssal sinus ; sur- 

 face radiately furrowed 

 and concentrically lined. 

 Type A. gigantea. 

 alata, Meek, 1872, (Ambo- 



nychia alata,) Proc. Acad. Nat. Sci. 



Phil., p. 319, and Ohio Pal., vol. 1, p. 



131, Hud. Riv. Gr. 



FIG. 777. Anomalodonta gigantea. Lfft valve, 

 showing hinge-line and muscular impression. 



gigantea, 8. A. Miller, 1874, Gin. 

 Quar. Jour. Sci., vol. 1, p. 17, Hud. 

 Riv. Gr. 



ANTHKACOMYA, Salter, 1861, Mem. Geo. Sur. 

 Gr. Brit. Iron Ores, pt. 3, p. 229. [Ety. 

 anthrax, coal ; Mya, a genus.] Equi- 

 valve, inequilateral, mytiliform ; liga- 

 ment external ; beak anterior ; hinge- 

 line straight ; no teeth ; surface 

 concentrically marked; shell composed 

 of an internal, lamellar, and subnacre- 

 ous layer, a thin layer of vertical pris- 

 matic shell, and an epidermis; struc- 

 ture similar to the Unionidse. Type A. 

 elongata. 



