16(S PROCEEDIXGS OF THE ACADEMY OF [1890. 



Capulus latus (Keyes.) 



Platyceraslahtin Keyes, 1888. Proc. Am. Philosophical Soc, vol XXV, p. 242, 

 figs. 10, 11. (Reprint., p. 14.) 



Platyccras latum Keyes, 1889. Proc. Acad. Nat. Sci., Philadelphia, 1889, p. 

 290. 



Capulus latus Keyes, 1890. Am. Geol., vol. V. 



Shell large, depressed, foniiiiig about one and one-half volutions, 

 very rapidly expanding from the apex to the aperture, l)ut enlarg- 

 ing transversely much more. than dorso-ventrally ; posterior side 

 comparatively very short. Apex small, incurved, but free from the 

 body of the shell and nearly in the same plane as the general curva- 

 ture. Aperture very large, campanulate, transversely elliptic ; lip 

 attenuate and slightly sinuous. Surface marked toward the aperture 

 by a few small nearly obsolete folds, and by numerous sinuous lines of 

 growth. 



Horizon and locality. Burlington limestone : Burlington, Iowa. 



This species is from the white compact layers of the upper division 

 of the Burlington beds. The specimens like the majority of fossils 

 from this stratum are usually more or less exfoliated. 



Capulus obliquus (Keyes). [Plate II, fig. ?>.] 



Platyccras obliqimni Keyes, 1888. Proc. Am. Philosophical Soc, vol. xxv, p. 

 241, figs. 12, 13. (Reprint., p. 13.) 



Platyceras obliqimm Keyes, 1889. Proc. Acad. Nat. Sci., Phila., 1889, p. 290 



Capulus obliquus Keyes, 1890. Am. Geol., vol. V. 



Shell of medium size, irregularly oblong, subspiral, forming one 

 volution ; regularly enlarging, slightly more rapidly transversely 

 than in the opposite direction, to the aperture. Apex large, obtuse, 

 ftir removed from the body of the sliell, which is broadly arcuate ; 

 very noticeably oblique to the plane of general curvature in the 

 body of the shell. Aperture irregularly quadrangular in outline ; 

 margin sharp and more or less sinuous. Surface marked by several 

 undefined longitudinal plications, which sometimes form longitudinal 

 series of obscure nodes ; these are crossed by numerous sinuous, often 

 subimbricated lines of growth. 



Horizon and locality. Burlington limestone : Burlington, Iowa. 



This species is a transition between the so-called " Orthonychia" 

 and " Platyceras" groups ; and is one of the few of this type occur- 

 ring in the American Carbonic. 

 Capulus quinoyensis (McChesney). [Plate II, fig. 9.] 



Platvceras quincyense McChesney, 1861. Desc. New Foss. Palte. Rocks West. 

 States, p. 90. 



