158 BULLETaOSf 181, UNITED STATES NlATIONlAiL MUSlEfUM 



Type: Filocyclus delphinulus (Mousson). 

 Distribution: Northern South America. 



FILOCYCLUS DELPHINULUS (Mousson) 



Plate 19, Figuees 10-12 



1869. Cyclopkorus delpJiinulus Mousson, Malak. Blatter, vol. IG, p. 180, 

 1875. Cyclophorus delphinulus Pfeiffee, Nov. Conch., vol. 4, p. 130, pi. 129, 



figs. 7-10. 

 1897. Amphicyclotus delpMnulus Kobelt and Moixendosff, Nachrb. deutschen 



malak. Ges., vol. 29, p. 139. 

 1912. Amphicyclotus delphinulus Kobelt, Martini-Chemnitz Conchylien Cabinet, 



vol. 1, sect. 19, p. 915, pi. 134, figs. 1-4. 



Shell broadly umbilicated, depressed-subdiscoid, spirally indis- 

 tinctly sulcate, whitish, with two bands, one above and the other below 

 the suture, which are dark brown and shining, and another chalky 

 zone below the suture. Spire elevated, the tip rather prominent and 

 horn colored. Suture subappressed, not deep. Wliorls 5.5, increas- 

 ing moderately in size, quite convex, flattened or subconcave at the 

 suture ; the last not descending, slightly concave above, then rounded, 

 not angulated, with the two cords on the umbilical wall, the space 

 between which is flattish and axially striate. Aperture scarcely 

 oblique, subcircular, angulated above, showing the banding within. 

 Peristome straight, acute, the margins approximated and joined by 

 a thin callus; the outer lip arched and protracted, angulated at the 

 posterior angle. The basal and columellar lip subsinuate, somewhat 

 obtuse. Umbilicus broadly open, equaling one-half the diameter of 

 the shell. Operculum corneous, thin, a little concave with closely 

 spaced ragged whorls. Height, 12 mm.; greater diameter, 20 mm.; 

 lesser diameter, 17 mm. 



The above is a translation of Mousson's description, to which he 

 adds: This species, for which we unfortunately have no definite 

 locality, resembles the peculiar C, cumingi Sowerby, but it is smaller 

 and has somewhat higher whorls but what peculiarly distinguishes 

 it from that is the coloring and sculpture. The first consists of a 

 soiled white base upon which 2 blackish brown shining zones are 

 present, the upper of which is more distantly removed from the 

 suture than is the case in cumingi. A chalk-white dull band is present 

 immediately below the suture, and the rest of the upper white sur- 

 face is dull. The entire surface is crossed by delicate spiral grooves 

 which are scarcely discernible on the dark bands. The whorls curve 

 slightly downward at the summit, toward the suture; and finally 

 the umbilical wall shows two threadlike cords separated by a flat or 

 slightly convex space. All the dull portion, particularly in the 

 region of the umbilicus, is marked by strong incremental lines. O. 



