Bkede.] Carbon/ 'fcm us Invertebrates. 89 



Length, 58 mm. ; width, 75 mm. ; convexity, 35 mm. A smaller 

 specimen : Length, 30 mm. ; width, 30 mm. ; length, 30 mm. ; 

 convexity, 23 mm. 



Range and distribution : L T pper Coal Measures ; Kansas City, 

 Turner, Lawrence, Lecompton, Topeka, Moline. 



This species can be distinguished from the previous by its 

 mesial sinus and corresponding fold of the dorsal valve, more 

 recurving beak, longer, more arched cardinal process, more 

 slender and elongate adductor markings on dorsal valve, and 

 also by the lateral ridges, which do not turn forward. 



There seem to be two forms of this species in Kansas : 

 One, a large, rather depressed shell, occurring in the lower part 

 of the Upper Coal Measures at Kansas City ; and the other, the 

 more common in the upper part of the stage, more narrow, gib- 

 bous and smaller. They may possibly prove to be varietally 

 distinct, occupying different horizons. 



AULACORHYNCHUS. 



Dittmar. Verhand. Kais. Min. Gesellsch. St. Petersburg, 2d ser., VIII, p. Q, pi. I, ff. 1-13, (1871). 

 Hall and Clarke, Pal. N. Y., VIII, pt. II, p. 311, (1893). 



Aulacorhynchus millipunctatus. Plate XI, fig. 6; plate XII, figs. 1, lb. 



Chonetesff miilipunetata Meek and Worthen, Proc. Acad. Nat. Sci. 



Phil., p. 35, 1870: Geol. Surv. 111., v, p. 566, pi. xxv, f. 3, ( 1873). 

 Tsogramma millipunctata Meek and Worthen, ibid., p. 568. 

 A ulacorhynchus millipunctatus Hall and Clarke, Pal. X. Y., vm, pt. n, 



p. 312, pi. lxxxiii, ff. 14, 15, (1893). 



Meek and Worthen's description : " Shell attaining a large 

 size, very thin, transversely subsemicircular, or more than 

 twice as wide as long, with lateral extremities rounded. Dor- 

 sal valve nearly fiat, or but slightly and evenly concave ; hinge 

 line a little less than the greatest transverse diameter ; car- 

 dinal process rather stout, with an obscure linear ridge (or 

 sulcus) extending forward from its base nearly to the front; 

 cardinal edge slightly thickened within so as to form a faintly 

 defined ridge extending about half way from the cardinal proc- 

 ess toward each lateral margin, but apparently without any 

 sockets for the reception of teeth in the other valve ; muscular 

 and other internal markings unknown ; surface ornamented 



