ART. IS A NEW FOSSIL GASTEKOPOD FROM ALASKA KIRK 6 



one extreme to the other. The largest specimen seen has six whorls, 

 and it is probable that this is near the maximum. 



The contours of the whorls are not easily seen owing to the super- 

 imposed cover of the marginal flange. The description as given is 

 based in part on cro&«-sections and in part on whorls from which the 

 flange has been removed. The Avhorls range from subcircuhir to 

 subovate in cross-section, the whorl being at times somewhat flat- 

 tened in the plane of the proximal portion of the marginal flange. 

 The whorls are closely appressed and overlap but slightly. The 

 inner upper margin of the whorl is somewhat flattened along the 

 contact zone Avith the superjacent whorl. The upper surface of the 

 whorl as far as the band is gently convex. From the lower margin 

 of the band the side of the whorl is nearly perpendicular as far as 

 the flange. Here there is at times a slight evagination of the 

 whorl. Below the flange there is a flattened area marking the con- 

 tact zone with the next succeeding whorl. The remainder of the 

 whorl is as a rule evenly rounded. 



The band, as noted under the description of the genus, is non- 

 typical, in that it does not have bounding carinae and the growth 

 lines in crossing it maintain their relative size and spacing. The 

 band is, however, quite as plainly marked as in some of the Pleuroto- 

 maridae. The band is wide and lies obliquely on the upper sloping 

 surface of the whorl. The lower margin of the band marks the 

 periphery of the whorl. So far as the specimens available for study 

 shoW' there is no slit. 



The growth lines on the upper surface of the whorl are sharply 

 flexed backward to the band, which they cross at right angles. 

 Below the band the growth lines are again sharply flexed backward. 

 On the flange the lines sweep outw^ard in a long smooth curve, in 

 the marginal portion of the flange apparently having a forward di- 

 rection. On the lower surface of the flange the growth lines parallel 

 the lines on the upper surface. On the whorl itself the lines hold the 

 same direction, but at a less acute angle. As shown by the growth 

 lines a deep V-shaped marginal notch was present, at the apex of 

 which lay the band. 



The flange has its inception at about one-third the height of the 

 whorl. At its base the flange is thick, tapering gradually to the 

 outer margin. When followed by another whorl the flange lies di- 

 rectly upon the infrajacent whorl and appears to have coalesced with 

 it. The flange lies in close contact with the whorl below, as far as 

 the upper margin of the band, from Avhich point it is free. In the 

 younger whorls the flange has no free extension, though this may be 

 due to breaking off of the fragile margin during the life of the animal. 

 In the later wdiorls it extends outward for a considerable distance. 



