178 PROCEEDINGS OF THE ACADEMY OF [1890. 



Platyceras nebrascense White, 1884. Indiana Geol. Rept. for 1883, p. 159, p. 

 xxxii, figs. 15 and 16. 



Capiihis pannis Keyes, 1890. Am. Geologist, vol. V. 



Shell small, broadly arcuate, or obliquely recurved, forming 

 nearly one volution ; regularly and rather rapidly expanding to the 

 aperture. Apex rather blunt ; inclined or recurved to the right. 

 Aperture ample, subovate; lip sharp, more or less regularly sinuous. 

 Surface nearly glabrate but under a glass showing numerous un- 

 dulating lines of growth, which are clearly visible nearly to the apex. 

 The shell is also marked sometimes by several almost obsolete 

 longitudinal folds. 



Horizon and localities. Upper Coal Measures : Indiana, Iowa, 

 Nebraska, Kansas and New Mexico. 



The small specimen figured (plate II, figs. 14a and 14b) is con- 

 sidered the type of Swallow's species, now in the museum of the 

 University of Missouri. A careful comparison shows the form de- 

 scribed from Nebraska by Meek is only a more mature individual of 

 C. parvus. Since, however, Sw^allow's species was poorly defined and 

 was never figured ; and'as Meek was the first to give a clear dignosis 

 of this form both by a full description and by good illustrations, it 

 is questionable whether Meek's name should not really be retained 

 for the form, Platyceras nebrascense having been almost universally 

 applied to this species as occurring throughout the west. 



Capulus spinigerus (Worthen). 



Platyceras spinigertts Worthen, 1873. Geol. Sur. Illinois, vol. V, p. 594, pi. 

 xviii, fig. 4. 



Capidus spinigerus Keyes, 1890. Am. Geologist, vol. V. 



Shell rather small, strongly arched ; composed of le.ss than one 

 volution ; very rapidly expanding to the aperture. Apex sharp, 

 scarcely incurved. Aperture subovate ; lip sinuous. Surface niarked 

 by many undulating, often somewhat imbricated lines of growth; 

 and also by a few scattering spines ; several low broadly rounded 

 longitudinal ridges have their origin near the apex and extend to 

 the aperture. 



Horizon and locality. Lower Coal Measures : Brighton, Illinois. 



This is one of the three spiniferous species of Capulus occurring 

 in the Carbonic strata of America. The other two are from the 

 Burlington limestone and have the spines arranged in longitudinal 

 series while in C. spinigerus the spines are scattered over the surface 

 of the shell. It is very probable that this form will prove to be 

 identical with C. trigonalis of Stevens. 



