Nezv Species of Devonian Fossils. 143 



Distemnostoma, n. gen. 



Diagnosis: Shell low to moderately high spired, consisting of 

 three to five or six volutions. Whorls deeper than wide, and 

 either rounded above or flattened to form a nearly horizontal 

 shoulder. Aperture higher than wide, with a broad notch and a 

 short slit at its top and a deep channel at its base. Slit-band 

 broad and situated entirely upon the upper side of the whorl. 

 The inner margin of the band lies along the median line of the 

 top of the whorl, and its outer margin is at least the width of 

 the band above the ambitus. Inner lip entire, thin. Umbilicus 

 narrow or lacking. 



Genotype: D. princeps, n. sp. 



The type of this genus resembles that of Omospira in its 

 flattened shoulder and in the high position of the band. It 

 appears to represent an entirely independent development, how- 

 ever, since its aperture was deeply channeled at the base, while 

 that of Omospira was rounded, and it had a slit and a true slit- 

 band, whereas Ulrich states that his genus had no slit. These 

 characters show important differences in the soft parts of the 

 animals' bodies. The above mentioned characters suffice to dis- 

 tinguish the genera, but in addition the band in the new genus is 

 even higher up on the upper surface of the whorl than in 

 Omospira. Indeed, in this respect it is distinguished from .all 

 other genera of its family. In most of the Pleurotomariidse the 

 band is on the side of the whorls and intimately related to some 

 peripheral angulation. In Omospira, it is seen to have moved to 

 the upper side of the shoulder, but here it reaches an extreme 

 of migration to the top of the whorl, when in D. princeps the 

 inner margin of the band is actually hid in the suture. 



Etymology: Sis, double, -(- tc/avw, to cut, -|- arofia, mouth. 



Distemnostoma princeps, n. sp. 

 Plate IV, figs. 18, 19 

 Description: Shell high-spired, consisting of four or five 

 gradually expanding volutions; apical angle about 65°. Whorls 

 subtriangular in cross-section, the upper surface flattened and 

 nearly horizontal, meeting the outer and inner sides in narrowly 

 rounded shoulders; sides depressed convex and converging 



