Bbepe.] Carboniferous Invertebrates. 163 



former being a little concave in outline, and the latter convex ; 

 extremities narrowly rounded. Beaks small, depressed, or ris- 

 ing little above the hinge line, very oblique, somewhat com- 

 pressed, incurved, and placed very near the anterior end ; 

 luinile apparently small and deep. Surface ornamented by 

 concentric strise of growth, and a few larger, obscure, concen- 

 tric wrinkles, crossed on the postero-dorsal region by five dis- 

 tinct, equidistant and radiating ridges, extending obliquely 

 from the beak to the posterior margin, the lower one being the 

 largest, and forming the umbonal ridge, while the upper one 

 runs parallel to the cardinal margin, and forms the edge of the 

 long corslet, or escutcheon. Length, about 1.10 inches ; height, 

 0.46 inch : convexity, near 0.43 inch." 



Range and distribution : Upper Coal Measures ; Kansas 

 City, Mo. 



I see no reason for putting this shell in a distinct species. 

 Our Kansas City specimens agree well with King's descrip- 

 tions and figures, being longer than Meek and AVorthen's fig- 

 ures. It seems that the principal reason for making a distinct 

 species of this shell was the fact that it came from a much 

 lower horizon than the European forms, but this is true of sev- 

 eral species of fossils which are common to the Coal Measures 

 of the Missouri valley and the Permian of Europe. The lines 

 of growth (or stria') on our specimens meet the hinge at a very 

 obtuse angle, while Meek's figure represents them meeting 

 nearly at right angles. In this respect it is like costatus: 



ASTARTELLA. 



Hall, Geol. Iowa, pt. II. p. 715. 



Astartella vera. Plate XXII, fig. 10. 



I ita ■■• 'in vera Hall, Geol. Iowa. pt. II, p. 715, pi. xxix, tf. la-c, (1858); 

 Keyes, Geol. Surv. Mo., v, p. 125, pi. xlvi, f. 6, (189.")): etc. 



Original description : tl Shell somewhat rhomboid-ovate, gib- 

 bous on the umbones ; beaks subanterior, elevated, approxi- 

 mate ; anterior end slightly concave below the beak and rounded 

 below, posterior end obliquely truncate. An oblique undefined 

 ridge extends from the beak to the posterior basal margin, hav- 

 ing the space between it and the ligamental area flattened ; 



