Nl^C. OBO.] 



BRACHIOPODA. 



355 



NUCLEOSPIRA, Hall, 1859, Pal. N. Y., vol. 3, 

 p. 219. [Ely. nucleus, kernel ; speira, 

 spire.] Shell spheroidal, or trans- 

 versely elliptical, more or less gibbous, 

 and furnished with spires as in Spirif- 

 era ; hinge-line short, cardinal ex- 

 tremities rounded, valves subequal, ar- 

 ticulating by teeth and sockets ; surface 

 smooth, structure punctate and cov- 

 ered with minute hair-like spines ; 

 ventral valve having the beak ex- 

 tended, with a triangular depression 

 beneath, on each side of which at the 

 base is a strong tooth, a narrow septum 

 from beak to base ; dorsal valve with 

 spatulate cardinal process, which bends 

 upward into the cavity of the opposite 

 beak; from the sides of this process 

 the brachial processes originate, which 

 support the spires; muscular imprints 

 confined to a narrow oval space. Type 

 N. ventricosa. 



barrisi, White, 1860, Bost. 

 Jour. Nat. Hist., vol. 7, 

 p. 227, Kinderhook Gr. 

 concentrica, Hall, 1859, 

 Pal. N. Y M vol. 3, p. 223, 

 Low. Held. Gr. 

 concinna, Hall, 1843, 

 ( Atrypaconcinna,) Geo. 

 4th Dist. N. Y., p. 200, 

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

 279, Hamilton Gr. 

 FIG. 586. - Nn- e legans, Hall, 1859, Pal. 

 cleosp.ra con- y ' ^ ^ p> ^ 



Low. Held. Gr. 

 pisiformis, Hall, 1859, (Orthis pisum, 



1852, Pal. N. Y., vol. 2,) Pal. N. Y., vol. 



3, p. 218, Niagara Gr. 

 rotundata, Whitfield, 1882, Desc. New 



Spec. Foss. from Ohio, p. 194, Low. 



Held. Gr. 



FH;. 587. Spiral coils of Nucleospira pisiformis. 



ventricosa, Hall, 1859, Pal. N. Y., vol. 3, 

 p. 220, Low. Held. Gr. This species 

 was first described in 1856, in 9th Reg. 

 Rep., as Spirifera ventricosa. 

 OBOLELLA, Billings, 1861, Pal. Foss., vol. 1, 

 p. 7. [Ety. diminutive of obolus, a 

 small Greek coin.] Shell ovate, circu- 

 lar or subquadrate, convex or plano- 

 convex ; ventral valve with a false 

 area, which is sometimes minute and 

 usually grooved for the passage of the 

 peduncle ; dorsal valve with or without 



ing muscular 

 impressions; 

 d, side view. 



an area; muscular impressions in the 

 ventral valve four, one pair in front of 

 the beak near the middle or in the 

 upper half of the shell, and the others 

 situated one on each side near the car- 

 dinal edge ; shell calcareous ; surface 

 concentrically striated. Type O. chro- 

 matica. 



ambigua, Walcott, 1885, Monogr. U. S. 

 Geo. Sur., vol. 8, p. 67, Chazy Gr. 



chromatica, Billings, 1861, Pal. Foss., vol. 

 1, p. 7, Up. Taconic. 



cingulata, Billings, 1861, Pal. Foss., vol. 

 1, p. 8, Up. Taconic. 



circe, Billings, 1871, Can. Nat. and Geol., 

 vol. 6, p. 219, Up. Taconic. 



crassa, Hall, 1847, (Orbicula c d 

 crassa,) Pal. N. Y., vol. I, /ff^ ft 

 p. 290, Up. Taconic Gr. \J y 



desiderata, see Elkania de- FlG 5g 8 _ Obol . 

 siderata. ella chroma! - 



discoidea, Hall & Whitfield, iea c.Show- 

 1877, U. S. Geo. Expl. 

 40th parallel, vol. 4, p. 

 205, Potsdam Gr. 



gemma, Billings, 1871, Can. Nat. and 

 Geol., vol. 6, p. 218, Up. Taconic. 



ida, Billings, 1862, Pal. Foss., vol. 1, p. 71, 

 Quebec Gr. 



misera, Billings, 1874. Pal. Foss., vol. 2, 

 p. 69, Up. Taconic. 



nana, Meek & Hayden, 1861, Proc. Acad. 

 Nat. Sci. Phil., p. 435, and Pal. Up. Mo., 

 p. 4, Potsdam Gr. 



nitida, Ford, 1873, Am. Jour. Sci. and 

 Arts, 3d ser., vol. 5, p. 213, Up. Taconic. 



polita, Hall, 1861, Geo. Rep. Wis., p. 24, 

 and Geol. Black Hills, p. 339, (Lin- 

 gula polita,) Potsdam Gr. 



pretiosa, Billings, 1862, Pal. Foss., vol. 1, 

 p. 68, Quebec Gr. 



transversa, see Linnarssonia transversa. 

 Obolellina, Billings, Dec., 1871, Can. Nat., 

 vol. 6, p. 220, syn. for Dinobolus. 



canadensis, see Dinobolus canadensis. 



galtensis, see Dinobolus galtensis. 



magnifica, see Dinobolus maguifieus. 

 OBOLUS, Eichwald, 1829, Zoologia Specialis, 

 vol. 1, p. 274. [Ety. obolus, a small 

 coin.] Shell orbicular, equilateral, 

 transverse or elongated, depressed ; 

 valves not articulated ; larger valve most 

 convex, beak obtuse or pointed, wide 

 flattened cardinal edge or false area, 

 over which the concentric lines of sur- 

 face growth pass uninterruptedly ; car- 

 dinal edge grooved longitudinalfy by a 

 semicylindrical furrow ; smaller valve 

 shorter, slightly convex, without prom- 

 inent beak ; hinge-linean arch ; cardinal 

 edge flattened, horizontally striated ; sur- 

 face smooth or having minute undulating 

 wrinkles ; interior of larger valve with 

 a mesial ridge, on each side of which 

 are two oval muscular scars, one pair 

 near the cardinal angles, the other 

 toward the center of the valve beyond 

 the mesial ridge ; structure calcareo- 

 corneous. Type O. apollinis. 



