132 BULLETIN 181, UTSTITED STATES NATTOaSPAL MUSEUM 



shades of brown. The nucleus consists of a little more than one 

 turn, which is small and well rounded. The next turn is marked 

 by very fine, retractively curved, closely spaced, almost hairlike 

 riblets, while the rest of the shell bears irregular rugations and 

 scattered malleations, the latter usually a little below the summit. 

 The rugations are strongest near the summit of the shell. Suture 

 well impressed. Periphery well rounded. Base well rounded, mod- 

 erately broadly umbilicated. The umbilicus is bounded by a strong 

 keel, which is strongly inpinched on the umbilical side and rendered 

 somewhat nodulose by the irregular axial sculpture. The umbilical 

 wall is marked by irregular axial ribs. Aperture large, subcircular, 

 except for an angulation at the posterior angle, feebly incised below 

 the summit on the outer lip and somewhat incised on the columellar 

 wall. Operculum typically cycladamsid. 



The two specimens figured, U.S.N.M. No. 356132, are part of four 

 from Mulgrave, St. Elizabeth Parish, Jamaica. I have selected these 

 to show the limit of variation in size and also in intensity of sculp- 

 ture. The larger has 5 whorls, the smaller 4.3. They measure, 

 respectively: Height, 13.3 and 9.2 mm,; greater diameter, 18.6 and 

 13,2 mm. ; lesser diameter, 14.0 and 10.2 mm. 



This species is easily distinguished from the other Cycladamsias 

 by its extremely reduced sculpture. 



Chitty cites Accompong Town, St. Elizabeth Parish, as type 

 locality. This appears to be the center of its distribution. Some 

 crab-carried ( ?) specimens were collected at Montego Bay, St. James 

 Parish. The living material seen extends from Mocho to Maggoty, 

 but we also have some dead specimens from 4 miles north of Black 

 River, St. Elizabeth Parish, and Glen Burnie Mountains, West- 

 moreland parish. 



This species presents a puzzle that will be cleared up only when 

 anatomic material comes to hand for dissection. There are two dis- 

 tinct sizes, a large and a small element. It is possible that these 

 may be sexual characteristics. The occurrence of both in the same 

 locality points toward such a condition. 



AusTROCYCLOTUS, new subgenus 



Aperostomine shells of helicoid shape the outside surface of which 

 is marked by closely placed threads crossing each other in protractive 

 and retractive series, producing an engine-turned pattern. 



Type: Aperostoma {Austrocy^clotus) stramineum (Reeve). 



Distribution: Panama to Ecuador and Venezuela and the West 

 Indies. 



The radula formula of Aperostoma (Austrocyclotus) grenadense 

 mcsweeni is 3:3:3:2. The jaw is without a median projection. 



