Heedk. ] Carboniferous Invertebrates. 105 



fold or sinus, but each sometimes slightly flattened in the mid- 

 dle near the front, where they meet without the slightest sinu- 

 osity in the margin of either. Beak of ventral valve small, 

 pointed, closely incurved upon that of the other valve, which is 

 but little less prominent ; foramen round and very small. Sur- 

 face with small, obscure, concentric marks of growth. Spiral 

 appendages each making about twelve turns. Surface (proba- 

 bly exfoliated ) showing only small, obscure, concentric ridges.' ' 

 Measurements, two specimens : Length, 10 mm., 10 mm. ; width, 

 11 mm, 13 mm. ; convexity, 6 mm, 5 mm. 



Range and distribution : Lower Coal Measures ; Fort Scott, 

 Marmaton station, Hourbon county, Prescott,. Linn county. 



This rare little fossil is rather variable in form. Most of our 

 specimens are rather more straight along the hinge than those 

 usually figured from this country, approaching, in this respect, 

 the form figured by C. Nikitin from the Upper Carboniferous 

 and Lower Permian of Europe, one specimen in particular be- 

 ing quite straight and wide along the hinge. The shells, in un- 

 worn specimens, show the surface fimbria 4 very well. 



SEMINULA. 



McCoy. Carb. Foss. Ireland, pp. 550, 558, (1844 I. 

 Hall and Clarke. Pal. N. Y., VIII, pt. II, p. 93, (1893) ; etc. 



Seminula argentea. Text fig. 3, ('. 



yv rt bratula argt ntt a Shephard, Amer. Jour. Sci., xxxiv, p. 152, f. 8, (1838). 

 Terebratula roinyi d'Orbigny [non L'Eveille), Voy. dans l'Ame'r. M<t. 



Pal., p. 46,(1842). 

 I • n bratula antisit nsis d'Orbigny, ibid., p. 4(5, | non 36). 

 /< /•< bratula peruviana d'Orbigny, ibid., pi. in, ff. 17-19, (non p. 

 Ti rt bratula tubtilita Hall, Stanbury's Expl. Gt. Salt Lake, p. 409, pi. iv, 



ff. 1, 2, ( 185-2 ) : etc. 

 Terebratula? subtflita Davidson, Mon. Brit. Carb. Brach., p. 18, pi. i, ff. 



21, 22, L857 ; etc. 

 Spirigera subtilita Meek and Hayden, Proc. Acad. Xat. Sri. Phil., p. 20, 



11859;: etc. 

 Athyris diffen ntis McChesney, New Pal. Foss., p. 47, (I860). 

 A thy r in mbtilita Newberry, Ives's Rep. Colo. Kiv. West, p. L26, i1861): 



Meek, Fin. Rep. U. S. Geol. Surv. Neb., p. 180, pi. i, f. 12, pi. v, f. 9, pi. 



vin, f. 4, (1872,: etc. 

 St ninula aubtilita Hall and Clarke Pal. X. Y., vm, pi. n. p. 95, IV. 66, 



07, p. 8(3, ff. 58, 59, pi. xi.vii, ff. 17 31, 1 1893). 

 Athyris (try ntea Keyes, Geol. Surv. Mo., v, p. 92, pi. xxxix, f. 11, 1 LE 

 y< minula argentea Schuchert, Bull. U. S. Geol. Surv. 87, p. .'577, | 1897), 

 8— vi 



