-TROPODA. 1O27 



phlld. ) 



layer. Thus, while the upper keel terminates anteriorly in a deep notch and the 

 growth lines curve backward strongly both from above and below in approaching 

 the keel in Ifflicotoma, they pass almost directly across the whorls in these Euomphali. 

 In passing over the keel they are but little, if at all, deflected, but a broad backward 

 sweep on the lower side of the whorls produces a slight obliquity of the aperture. 



Jn stating the differences in the direction of the lines of growth of the Carbon- 

 iferous and Lower Silurian shells just compared, we were careful to say, "the 

 surface of the outer layer," because we have reason to believe that the markings of 

 the inner layer are not the same as those of the outer. We have before us a 

 remarkable specimen of an undescribed Euomphalus from the oolitic limestone of 

 the Upper Coal Measures at Kansas City, Missouri. The species is closely related 

 to and perhaps not specifically distinguishable from the Chester group shell to which 

 Meek and Worthen have given the name E. planidorsatus. There is no doubt then 

 about its genetic relations. The specimen in question has the external layer of the 

 shell peeled off in patches so as to expose the inner layer. Iloth layers show lines 

 of growth very distinctly, and it was in comparing their respective directions in the 

 region of the upper keel that we met with a surprise. On the outer layer, namely, 

 the stria) pass almost straight from the suture to the keel, beyond which they turn 

 first very gently forward and then more strongly backward into the broad basal 

 sinus. The inner layer seems to be composed of short overlapping lamina;, the 

 edges of which impressed themselves upon the internal cast as closely arranged 

 parallel grooves. The latter, instead of being direct like the lines of the outer layer, 

 curve backward strongly in passing over the region of the keel, thus indicating a 

 very decided > -shaped notch in the lip, which must, however, have been confined 

 to the inner layer of the shell. Immediately beneath the keel the test is thick 

 enough to produce a faintly concave instead of convex band on the interior cast. 



After seeing this specimen, the important question arises, do not the same 

 conditions pertain to all the similarly carinate Euomphali? Unfortunately we have 

 no positive data bearing upon the question, although we have seen specimens of 

 other species in a similar state of preservation; but the specimen described is the 

 only one showing any sign of transverse markings on the inuer surface of the shell, 

 the casts in every other instance being quite smooth. Still, the Kansas City speci- 

 men proves that a notched aperture may really exist in species of Euomphalus 

 exhibiting no external sign of its presence, and this fact is, to say the least, worthy 

 of being remembered. 



In addition to the euomphaloid types discussed on the foregoing pages, we 

 distinguish three others, two of them under new names, the third described and 

 named Eccyliopterus by Kemele. 



