PEN.] 



BRACHIOPODA. 



361 



Fig. 595.— Pentamerella 

 arata. Side view. 



merw.~\ Ventral valve gibbous, beak 

 incurved, fissure triangular, area nar- 

 row, mesial sinus ; in the interior an 

 elongate, spoon-shaped pit, the upper 

 part supported on a central septum ; 

 dorsal valve convex, mesial fold ; crura 

 conjoined at their bases, making a 

 V-shaped pit, which is attached to the 

 valve in its upper part, and continues 

 sessile for about half the length of the 

 shell ; surface plicated. Type P. arata. 

 arata, Conrad, 

 1841, (Atrypa 

 arata and At- 

 rypa octo-cos- 

 tati,) Ann. 

 Rep. N. Y., p. 

 55, and Pal. N. 

 Y., vol. 4, p. 

 375, Schoharie 

 grit and Up. 

 Held. Gr. 

 compressa, Ring- 

 ueberg, 1886, 

 Bull. Buf. Soc. 

 Nat. Sci., vol. 

 5, p. 15, Niag- 

 ara Gr. 

 dubia, Hall, 1860, 

 (Spirifer du- 

 bius,) 13th 

 Rep. N. Y. St. 

 Mus. Nat. Hist., p. 90, Ham. Gr. 

 micula, Hall, 1867, Pal. N. Y., vol. 4, p. 



378, Ham. Gr. 

 obsolescens, Hall, 1867, Pal. N. Y., vol. 



4, p. 379, Devonian, 

 papilionensis, Hall, 1858, (Pentamerus 

 papilionensis,) Geo, Rep. Iowa, vol. 1, 

 pt. 2, p. 514, Ham. Gr. 

 Pentamerus, Sowerby, 1812, Min. Conch., 

 vol. 1, p. 73. [Ety. penta, five ; meros, 

 apartments.] Shell globose, ovate, re- 

 ceiving valve largest; generally desti- 

 tute of mesial fold and sinus, but when 

 present, the fold is in the receiving, 

 and the sinus in the entering valve ; 

 no hinge-line ; area large, undefined, 

 and having a deep, triangular pit in the 

 center, under the beak of the dorsal 

 valve, and into which the beak of the 

 entering valve is strongly incurved ; 

 internally the receiving valve has one 

 large bipartite central septum, the walls 

 of which suddenly divaricate as they ap- 

 proach the entering valve, forming the 

 walls of the external triangular open- 

 ing, and inclosing between them a 

 triangular chamber much smaller than 

 the two lateral ones ; in the entering 

 valve the two corresponding plates are 

 subparallel, and separate from their 

 origin, being so curved that internal 

 casts show one of their edges, like the 

 diverging cardinal teeth of Orthis, and 

 the inner edges form the long, subparal- 

 lel slits, the middle one of the three re- 

 sulting chambers being much the nar- 

 rower. Type P. knighti. 



aratw, see Pentamerella arata. 



arcuosus, McChesney, 1861, New Pal. 



Foss., p. 87, Niagara Gr. Not recog- 

 nized, 

 barrandi, Billings, 1857, Rep. of Progr., 



Geo. Sur. Can., p. 296, Mid Sil. 

 beaumonti, Castelnau, 1843, Syst. Sil., p. 



38. Not recognized, 

 bisinuatus, McChesney, 1859, New Pal. 



Foss., p. 85, and Trans. Chi. Acad. Sci., 



vol. 1, p. 30. Niagara Gr. 

 borealis, Meek, 1868, Trans. Chi. Acad. 



Sci., p. 95, Ham. Gr. This name was 



preoccupied by Eichwald in 1840. 

 brevirostris, Sowerby, 1839, (Terebratula 



brevirostris, ) Murch. Sil. Syst., p. 631, 



and Pal. N. Y., vol. 2, p. 278. Niag- 

 ara Gr. 

 chicagoensis, Winchell & Marcy, 1865, 



Mem. Bost. Soc. Nat. Hist, p. 94, Niag- 

 ara Gr. 

 comis, Owen, 1852, (Atrypa comis,) Geo. 



Sur. Wis., Iowa and Minn., p. 583, 



Ham. Gr. 

 coppingeri, Etheridge, 1878, Quar. Jour. 



Geo. Soc, vol. 34, p. 593, Up. Silurian. 

 crastiradiatm, McChesney, 1861, New Pal. 



Foss., p. 87, Niagara Gr. Not recognized. 

 deshayexi, Castelnau, 1843, Syst. Sil., p. 



38. Not recognized. Probably syn. for 



Amphigenia elongata. 

 elcmgatus, see Amphigenia elongata. 

 fornicatus, Hall, 1852, Pal. N. Y., vol. 2, 



p. 81, Clinton Gr. 

 galealifoi-mis, Meek & Worthen, syn. for 



P. galeatus. 

 galeatus, Dalman, 1827, (Atrypa galeatus,) 



Vet. Acad. Handl., p. 130, and Pal. 



N. Y., vol. 3, p. 257, Low. Held Gr. 

 intralineatus, Winchell, 1866, Rep. Low 



Penin. Mich., p. 94, Ham. Gr. 

 knappi, Hall & Whitfield, 1872, 24th Rep. 



N. Y. St. Mus. Nat. Hist., p. 184, Niag- 

 ara Gr. 

 knighti, Sowerby, 



1812, Min. 



Conch., vol. 1, 



p. 73, Devonian, 

 laqueatus, Con- 1 



rad, 1855, Proc. 



Acad. Nat. Sci., 



p. 441, Niagara 



Gr. 

 lenticul aris, 



White & Whit- 

 field, 1862, Proc. 



Bost- Soc. Nat. 



Hist., vol. 8, p. 



295, Kinder- 

 hook Gr. 

 littoni, Hall, 1859, Pal. N. Y., vol. 3, p. 



262, Low. Held, and Niagara Gr. 

 lotis, Walcott, 1885, Monogr. U. .S. Geo. 



Sur., vol. 8, p. 161, Devonian, 

 multicostatus, Hall, 1861, Rep. of Progr. 



Wis. Sur., p. 1, Niagara Gr. 

 nucleus, Hall & Whitfield, 1872, 24th 



Rep. N. Y. St. Mus. Nat. Hist., p. 20 0, 



Niagara Gr. 



Fio. 596.— Pentamerus 

 knighti. 



