Bkkde.J Carboniferous Invertebrates, 87 



to and a little in front of the hinge nearly to its extremity, 

 where it turns abruptly forward, forming a margin to the vis- 

 ceral area, and disappearing about the middle. Mesial ridge 

 distinct, broad posteriorly, narrowing and rising to the end, 

 which is two-thirds the distance to the anterior margin. Ad- 

 ductor scars distinct, the two nearly forming a circle or broad 

 ellipse, ending in an elevated anterior lobe. Scars placed well 

 to the posterior. Brachial markings very indistinct, beginning 

 at anterior end of adductor scars and extending outward, as 

 nearly as can be made out, similarly to those of the preceding 

 shell. "The remainder of the interior covered with pustules. 

 Surface of both valves ornamented by small, rather obscure, 

 more or less regular concentric wrinkles, and covered by numer- 

 ous small, short, rather appressed spines, which are larger on 

 the ventral valve where they are often connected with little, 

 sometimes elongated tubercles." Measurements: Length, 40 

 mm. ; width, 59 mm. ; convexity, 25 mm. 



Range and distribution : Upper Coal Measures ; Kansas City, 

 Lawrence, Topeka. 



This species can be distinguished from the preceding by the 

 less convex pedicle valve, which has no sinus, narrower con- 

 centric wrinkles, and the fact that it has but a single set of 

 spines, which are small and appressed. In some respects this 

 species is intermediate between the one preceding and the fol- 

 lowing, and is sometimes hard to distinguish from them with- 

 out good specimens. 



Productus punctatus. Plate X, figs. 3-3e: plate XI, fig. 3. 



Aiiomitcs punctatus Martin, Petref. Derb., pi. xxxvn, f. G, (1809). 

 Productus punctatus? Morton, Amer. Jour. Sci., xxix, p. 153, pi. xxvi, 



f. 38, (1836). 

 Productus punctatus Shumard, Marev's Rep. U. S. Expl. Red Riv. 



Louis., p. 201, pi. r, f. 5, pi. II, f. 1, (1853): Meek, Fin. Rep. U. S. Geol. 



Surv. Neb., p. 169, pi. n, f. 6, pi. iv, f. 5, (1872); etc. 

 Productus 8< mi punctatus Shephard, Amer. Jour. Sci., xxxiv, f. 9, ( 1853 1. 

 Productus tutfulospinus McChesney, New Pal. Foss., p. 37, (1860). 



Meek's description (in part) : " Shell attaining a rather large 

 size, thin, varying from rotund-subquadrate to longitudinally 

 subovate, being sometimes wider than long, and in other ex- 



