80 THE NAUTILUS. 



irregularity in the different specimens I should have been more 

 cautious, but this was not the case in this instance. However, 

 a year or two later another batch was received, and this time 

 the "shells" were no two alike, and most of them with com- 

 paratively little resemblance to a normal shell. 



The blunder was clear. These specimens were secretions 

 from the bases of the Actinias, but how the first lot attained the 

 regularity shown by the figures is still a mystery. The readers 

 of this article must assess my culpability. 



NENIA COOKI N. SP. (PLATE VII, FIGS. 11,12, 13.) 



BY H. A. PILSBRY. 



The shell is thin, obesely fusiform, the diameter contained 

 about 2 times in the length, composed of six whorls, the first 

 H strongly convex. The first four whorls form a rapidly en- 

 larging cone ; the next whorl is much inflated ; and the last 

 whorl is large, somewhat flattened peripherally in its first half, 

 then rapidly contracting, concave a short distance below the 

 suture; the neck rounded and shortly descending, free in front. 

 Surface mat. of a chamois tint, but darker on the antepenult, 

 paler on the last whorl; covered with a very thin cuticle. The 

 apex is entire, obtuse. First whorl smooth, the next having 

 delicate striae; on the third whorl low, coarse wrinkles appear, 

 and the following whorls have coarse sculpture of irregular, re- 

 tractive wrinkles. On the neck they become sharper, more 

 crowded, and less oblique to the growth lines. The aperture is 

 but slightly longer than wide, rounded, ivory-yellow within. 

 Peristome^broadly expanded, faintly flesh-tinted within, with a 

 narrowly reflexed white edge. The superior lamella is high, 

 sinuous, continuous with the spiral lamella. The inferior 

 lamella is strongly developed. Subcolumellar lamella is deeply 

 immersed. The principal plica is lateral, running in to the 

 middle of the dorsal side, where its inner end is closely con- 

 tiguous to the upper end of the lunella. The lunella is cres- 

 centic, deeply curved, and wholly visible in the aperture (seen 

 foreshortened in fig. 11). 



