NO. 1520. 



NEW YITRINELLW MOLLUSKS—BARTSCH. 



173 



The t3q3e, which is one of these specimens, has 3f whorls and measures: 

 Greater diameter 1.0 mm.; lesser diameter 0.8 mm.; altitude about 

 0.25 mm. 



CIRCULUS COSMIUS, new species. 



Shell decidedly depressed, planorboid, creamy white, shining. Nepi- 

 onic whorls 2, well I'ounded. helicoid, polished. Succeedino^ turns 

 marked by a low, rather broad spiral thread at the summit and a 

 strong-, acute, lamellar ridge at the periphery, and another equally 

 strong- halfway between the periphery and the summit. The last has 

 the free edge pointing- outward, forming- an angle of 45-^ with the pe- 

 ripheral lamella. The spaces between these keels are gently rounded 

 and marked by incremental lines only. The middle keel forms the 

 most eleyated portion on each whorl, the summit of the whorl at the 

 suture being- considerably lower. Base yery broadly umbilicated, 

 marked by a spiral, lamellar carina, wiiich is as strong as the peripheral 

 one and is situated halfway between this and the umbilical angle. In 

 addition to this carina the entire base shows line incremental lines. 



Fig. 8. — CiRcuLus cosmtus. a, top view: b. side view; c, basal view. 



Umbilicus limited by an ol)tuse ang-le; columellar wall almost yertical, 

 marked ])y three slender, equally spaced, spiral lirations. Aperture 

 decidedly oblique, pentagonal, the angles being formed hy the three 

 carinfe, the posterior angle of the aperture, and the umbilical angle; 

 outer lip thin; columella decidedly curyed; parietal wall coyered by a 

 .strong- callus, which renders the peritreme almost continuous. 



There are two specimens in the collection of the U. S. National 

 Museum, Cat. No. 192708, both dredged by the U. S. Bureau of 

 Fisheries steamer Albatross, at Station 2799, near Atacames, Ecuador, 

 in 29^ fathoms of water. The type, which is one of these two speci- 

 mens, has ii whorls and measures: Greater diameter, 2.5 mm.; lesser 

 diameter, 2.1 mm.; altitude, 1 nun. 



CIRCULUS CERROSENSIS, new species. 



Shell decidedly depressed, })lanorboi(l, semitransparent, yellowish 

 horn colored. Nepionic whorls 2. moderately eleyated, polished. Suc- 

 ceeding- turns marked by a feeble spiral thread at the summit and a 

 strong, acute spiral lamella at the peripher}- and another equally strong 



