92 BULLETIN 181, UNITED STATES NATIONAL MUSEUM 



rounded. Base well rounded, openly umbilicated, with a strong keel, 

 which is not only pinched in on the umbilical side, but appears even 

 excavated at this place. On the outside of the keel there is also a 

 depression and here we find strongly developed pits and nodules 

 which extend over the anterior half of the base. The umbilical 

 wall is marked by somewhat irregular riblets and lines of growth. 

 Aperture circular, strongly protracted and angulated at the posterior 

 angle ; outer lip of the peristome thin ; the inner somewhat thickened. 

 The operculum differs from the typical ptychocochlid in having the 

 outward reflected portion of the whorls not quite touching that of the 

 expanded inner portion of the succeeding turn, thus leaving a slight 

 channel between the two in some of the turns. 



The type is one of C. B. Adams' complex of Gyclostoma varians. 

 It is part of his No. 7 and is labeled Portland, Jamaica, Agnes Hines, 

 collector. 



The type is in the Amherst College collection. It has 5 whorls and 

 measures: Height, 22.8 mm.; greater diameter, 31.4 mm.; lesser 

 diameter, 23.0 mm. 



PTYCHOCOCHLIS SENEX, new species 

 Plate 14, Figures 22-24 



This is the largest of the known Jamaican cyclophorids. It has a 

 helicoid shell. The specimen is without periostracum. The nucleus 

 consists of a little more than one turn, which is well rounded and 

 smooth. The postnuclear whorls are well rounded; the first 2.5 are 

 marked by slender, slightly retractively curved, hairlike axial rib- 

 lets, which are not quite so wide as the spaces that separate them. 

 These are followed by a turn in which very strong, retractively 

 curved ridges are present. On the first half of the last whorl these 

 ridges assume an arrowpoint arrangement, a cone-in-cone type, in 

 which the point of the arrow is almost on the middle of the whorl. 

 On the last half of the last whorl this arrangement becomes obsolete 

 and the shell is marked by strong incremental lines and nodulations 

 near the summit, the senescent last portion appearing strongly den- 

 ticulated. The suture of the early whorls is well impressed, while 

 on the last turn the summit of the whorls becomes appressed to the 

 preceding turn, and materially creeps up on this. Periphery well 

 rounded. Base well rounded, openly umbilicated with a strong, 

 heavily nodulose keel marking the outer limit of the umbilicus. 

 From this keel there radiates toward the middle of the base a series 

 of heavy ridges which are separated by spaces about as wide as the 

 ridges. These ridges have a protractive slant. They become obso- 

 lete on the last fifth of the last whorl. The umbilical wall is marked 

 by coarse ribs, which bear finer hairlike incremental lines. Aper- 



