Bekde.] Carboniferous Invertebrates. 143 



AVICULOPINNA. 



Meek. Amer. Jour. Sci., XLIV, p. 282, ( 1S67). 



Aviculopinna americana. Plate XVIII, fig. 2. 



Avicuht pinner form is Geinitz, Carb. u. Dyas in Neb., p. 31, pi. n, f. .13, 



(not S. pinncef omnia Geinitz, 1848), (1866). 

 Aviculopinna americana Meek, Amer. Jour. Sci. ser. n, xliv, p. 282, 



(1867); Fin. Rep. U. S. Geol. Surv. Neb., p. 197, pi. ix,ff. 12a-d, (1872); 



Pal. Ohio, ii. p. 337. pi. xx, f. 2, (1875); Herrick, Bull. Den. Univ., n, 



p. 38, pi. i, f. 20, i 1887); Keyes, Geol. Surv. Mo., v, p. 115, (1894). 



Meek's description : " Shell small, compressed, with the slen- 

 der elongated form of some of the Carboniferous species of Pinna ; 

 cardinal and ventral margins generally nearly straight (the 

 latter being more convex in outline) and converging gradually 

 from behind to the rather obtusely pointed anterior extremity ; 

 posterior side truncated, rounding into the base, and inter- 

 secting the posterior extremity of the hinge very nearly at 

 right angles — a little sinuous just below the extremity of the 

 hinge. Cardinal margin so slightly convex in outline as to ap- 

 pear quite straight, very nearly equaling the greatest length of 

 the valves, and provided with a well-developed marginal ridge, 

 which narrows to a mere line, or dies out before reaching the 

 beaks, and widens gradually to the posterior extremity. Beaks 

 nearly or quite obsolete, extremely oblique, and very slightly 

 behind the very narrow, obtusely pointed, anterior extremity. 

 Surface with two or three broad, nearly obsolete radiating 

 ridges on the posterior dorsal region, and ornamented by nu- 

 merous slender, very regularly disposed and abruptly elevated 

 lines or lamellae, much narrower, than the spaces between, and 

 curving gracefully parallel to the posterior border, while on 

 the basal half of the valves they are closely approximate and 

 curved forward." 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Lansing (Leavenworth county), Topeka. 



Aviculopinna illinoiensis. Plato XVII, figs. 1-lc. 



Aviculopinna illinoiensis \Vorth»n, Bull. No. 2 111. St. Mus. Nat. Hist., 

 p. 13, (1884): Geol. Surv. 111., vin, p. 128, pi. xx, ff. 5, 5a, (1890). 



Shell of medium size, both valves convex; dorsal and ventral 

 margins moderately curved, converging at an angle of about 

 20 . Beak very small and indistinct but placed about as in 



