ANA.] 



BRA CHIOPODA. 



333 



pressed convex, the spires lie in the 



ventral valve. Type A. umbonata. 

 timbriata, Claypole, 1883, Proc. Am. Phil. 



Soc., p. 232, Portage Gr. 

 gemmula, syn. for Spirifera planocon- 



vexa. 

 gregaria, Hall, 1860, 13th Rep. N. Y. St. 



Mus. Nat. Hist., p. 81, and Pal. N. Y., 



vol. 4, p. 261, Chemung Gr. 

 minuta, White, 1862, Proc. Bost. Soc. 



Nat. Hist., vol. 9, p. 26, Waverly Gr. 

 nucleus, syn for Ambocoelia umbonata. 

 praeumbona, Hall, 1857, (Orthis praeum- 

 bona,) 10th Rep. N. Y. St. Mus. Nat. 



Hist., p. 167. and Pal. N. 



Y., vol. 4, p. 262, Ham. 



Gr. 

 subumbona, see Spirifera, sub- 



umbona. 

 umbonata, Conrad, 1842, FIG. 534 -Am- 



(Orthis umbonata,) Jour, bocceiiaum- 



Acad. Nat. Sci., vol. 8, p. bonata ' 



264, and Pal. N. Y., vol. 4, p. 259, Mar- 



cellus Shale and Ham. Gr. 

 unbonata var. gregaria, see A. gregaria. 



AMPH IGENI A , 

 Hall, 1867, 

 Pal. N. Y., 

 vol. 4, p. 

 382. [Ety. 

 amphi, on 

 both sides ; 

 g en e a , 

 growth. ]In- 

 equiva 1 v e , 

 oval, ovoid, 

 or subtri- 

 a ngu lar , 

 more or less 

 convex, 

 wi t hout 

 mesial fold 

 or sinus ; 

 valves ar- 

 ticttla ting 

 by teeth and 

 sockets, 

 without 

 area ; den- 

 tal lamellae, 

 in the ven- 

 tral valve, 



PIG. 535. Amphigenia 

 elongata. 



c o n o ne 



on their dorsal sides, forming an 

 angular pit, which opens by a tri- 

 angular fissure beneath the beak, 

 and in its anterior extension is sup- 

 ported on a central septum ; dorsal 

 valve with a thickened cardinal pro- 

 cess bordered by teeth sockets anchy- 

 losed to the bottom and supporting the 

 crura, which extend into the cavity of 

 the shell. Type A. elongata. 



curta, Meek & Worthen, 1868, (Strick- 

 landinia elongata var. curta,) Geo. 

 Sur. 111., vol. 3, p. 402, Oriskany sand- 

 stone. 



elongata, Vanuxem, 1842, (Pentamerus 

 elongata,) Geo. 3d Dist. N. Y., p. 132, 



and Pal. N. Y., vol. 4, p. 383, Schoharie 

 grit and Up. Held. Gr. 



FIG. 536. Amphigenia elougata. 



elongata var. undulata, Hall, 1867, Pal. 

 N. Y., vol. 4, p. 384, Up. Held. Gr. 



elongata var. subtrig- 

 onalis, Hall, 1857, 

 (Meganteris subtrig- 

 onalis,) 10th Rep. 

 N. Y. St. Mus. Nat. 

 Hist., p. 123, Up. 

 Held. Gr. 



ANASTROPHIA, Hall, 

 1867, Pal. N. Y., 

 vol. 4, p. 373. [Ety. 

 ana, with ; strophe, a 

 turning round ; the 

 relation of the 

 valves is the re- 

 verse of that of 

 Pentamerus.] Gib- FIG. 

 bous ; ventral valve nia elongata. 

 the smaller, gibbous in its upper part, 

 depressed or sinuate below, with the 

 V-shaped pit sessile for nearly its entire 

 length ; small flattened space on each 

 side of the fissure; dorsal valve ven- 

 tricose, with prominent umbo ; hinge- 

 plate extended in gradually converging 

 vertical lamellae which are joined to the 

 shell throughout their length, while the 

 crura are extended into the cavity, in 

 thin free lamellae. Type A. verneuili. 



Amphige- 



FIG. 538. Anastrophia iuternnscens. 



internascens, Hall, 1879, 28th Rep. N. Y. 

 St. Mus. Nat. Hist., p. 168, Niagara Gr. 



