1888.] NATURAL SCIENCES OF PHILADELPHIA, 239 



toward the suture. The number of raised revolving lines appears to 

 vary with the size of the specimens, and the maximum given is for 

 the largest specimens collected. This species was originally de- 

 scribed from Pasey county, Indiana, and Grayville, Illinois. 



Pleurotomaria carbonaria Norwood and Pratten. 



Pleurotoviaria carbonaria Norwood and Pratten, 1855. Jour. 

 Acad. Nat. Sci. Phila., (2), vol. Ill, p. 76. 



This is by far the largest gasteropod yet discovered at Des Moines, 

 and the test, as compared with that of the associated species, is ex- 

 tremely thick and heavy. A closely allied species has been described 

 from the coal measures at Newport, Indiana, as P. newporteusis 

 White. According to Dr. White it differs from P. carbonaria in 

 having " its revolving band ample and raised instead of concave, 

 with revolving lines within it, as in that species ; and also in having 

 its aperture subcircular instead of semicircular." 



Macrocheilus humilis, nov. sp. (Plate XII, fig. 1.) 



Shell very small, short, subfusiform, or elongate-subovate ; spire 

 j)rominent, forming one-third or more of the entire length of the 

 shell ; volutions about six, increasing moderately in size, slightly 

 convex. Test rather thin. Columellar fold distinctly visible within 

 the aperture, which is subelliptical ; callosity clearly defined but 

 not conspicuous ; outer lip thin, sharp. Suture well-defined but 

 not deeply impressed. Surface smooth, but under a glass exhibiting 

 lines of growth. Length 6 mm. ; width 3'5 mm. 



This little species is from the superimposing black shales of coal 

 No. 3, at the Giant mine ; and is found associated with the numerous 

 other small gasteropods mentioned hereafter, 



Macrocheilus gracilis Cox. 



Macrocheilus gracilis Cox, 1857. Geol. Sur, Kentucky, vol. III, 

 p. 570, 



The roof shale of coal No. 3, has furnished a good series of this 

 species, representing all stages of development up to those fifteen 

 millimetres in length. The smaller specimens are less ventricose 

 and have the spire proportionally higher than in the older ones, 

 which approach nearer the form described as M. ventricosus Hall, 

 and there is therefore reason to believe that the two species will 

 eventually prove identical. Cox states in his description that his 

 .species was most likely a young shell. White^ considers Soleuiscus 



1 Geol. Ind., Rep. for 1883, p. 155. 



