534 PROCEEDINGS OF THE ACADEMY OF [Sept., 



PtychococJUis is a somewhat difficult group in the present condition 

 of the literature. Chitty's monograph is not all that could be desired; 

 yet his major grouping of the species by characters of the operculum is 

 doubtless sound. 



The species long known as " jamaicensis Chemnitz" is certainly not 

 the Chemnitzian form, which was really portlandcnsis of Chitty. As 

 Chemnitz was not binomial, this use of the name was of no effect. 

 " Cyclostoma jamaicensis" next figured in the supplement of Wood's 

 Index Testaceologicus, but the figure given defies identification, and 

 may or may not represent the jamaicensis of Sowerby's Thesaurus 

 Conchyliorum, where the first recognizable, though not veiy good, 

 figures are given. We would therefore call the species Aperostoma 

 jamaicensc (Sowerby). 



Aperostoma (Ptychocochlis) lacteofluviale a. sp. 



The shell is umbilicate, the umbilicus contained 5^ times in the 

 diameter; rather depressed, the height two-thirds the diameter; 

 solid, covered with a chestnut cuticle. The spire is low and small; 

 whorls 4J, very convex, very finely striate radially, the first If nearly 

 smooth. Small waves then appear, at first radial in direction, but 

 after 2A whorls they become strong, regular, protractive, not reaching 

 either suture. After the first third of the last whorl the waves weaken 

 and are replaced by ill-defined depressions longer in the spiral direction. 

 At the periphery and base there are a few inconspicuous, coarse spirals. 

 The basal keel is low, defined by a depression within, and sometimes 

 with a few pits outside. The aperture is oblique, rotund, angular 

 above, reddish-brown within, the lip whitish, outer and inner margins 

 about equally curved. Alt. 10.5, diam. 16 nun. 



The operculum is rather strongly concave outside, and bears a spiral 

 lamella which makes 7 turns and terminates in a central pit as usual. 

 At the outer whorls, the edge of this lamina is reflexed outwardly and 

 flattened, almost meeting across the interval. Inside it is yellow and 

 slightly convex. Diameter 5 mm. 



Round Hill, Milk River, Clarendon, the types No. 101,193, A. N. 

 S. P., received from Mr. George H. Clapp. 



This is a species of Chitty's group 1, somewhat related to A. notatum 

 Chitty, but distinct in sculpture, etc. 



Aperostoma (Ptychocochlis) tryonianum a. sp. 



The shell is rather openly umbilicate, the diameter of the umbilicus 

 half the width of the aperture; height about 70 per cent, of the diam- 

 eter; white under a thin yellow cuticle which has a tendency to be 



