MOLLUSCA FROM JUAN FERNANDEZ AND EASTER ISLAND 223 



13, 1 891), but it differs distinctly in colour and sculpture from every species 

 of the genus hitherto known from the Peruvian region. 



Lunatia pisiformis Recluz. — Masatierra, 20 — 35 m, sand and Corallina, 



3 sps., max. h. 6 mm; wh. 4 V2 (^V4); Cumberland Bay, many sps., max. h. 

 5,7 mm (V12 1916); same locality, 30 — 40 m, 2 small shells (V4 1917). Previously 

 known from Valparaiso (Tryon; Reeve). 



Littorina inauritiaiia Lamarck. — Masafuera, stones on the shore, many 

 sps., max. h. 18 mm. Distribution from Mauritius to N. Zealand (Tryon, 1887, 

 Man. of Conch. IX). 



Trifora basalis n. sp. PI. 8, fig. 7. — Shell elongate, uniformly grayish- 

 white. (Nuclear whorls broken off.) Postnuclear whorls slightly convex; suture 

 strongly impressed, marked by a fine thread. Sculpture consisting of 3 revolving 

 riblets on each whorl, the uppermost narrower than the others in the 3—4 first 

 postnuclear whorls, than equal in strength, crossed by strong axial ribs, forming 

 rounded knobs in the crossing points and squarish pits in the interstices; 

 microscopically reticulated of spiral and longitudinal striae; axial riblets in the 

 third whorl 16, in the 4th 18, and in the penultimate 20. Last whorl beneath 

 the three rows of knobs with a basal smooth keel, and, on its evenly rounded 

 base, with 4 further similar ones, all separated by furrows narrower than the 

 keels and finely sculptured by transverse striae. Aperture pear-shaped, colu- 

 mella concave, canal as long as the aperture. Dimensions: height 6,3, h. of 

 aperture 1,7, breadth 2 mm. Postnuclear whorls 7 ^Iz. 



Masatierra, 20—35 m, sand and Corallina, i somewhat worn and frag- 

 mentary shell (apex and outer lip broken off), V* 1917- The shell is similar 

 to T. galapagensis Bartsch 1907^, which has, however, only 3 basal ridges and 

 a different sculpture in the uppermost postnuclear whorls. 



Cerithiopsis dispar n. sp. PI. 8, fig. 8. — Shell turrited, dark-brownish 

 with lighter nodules; whorls convex, suture channelled, marked with a fine 

 thread. Nuclear whorls 2, smooth; postnuclear whorls 12, sculptured with 3 

 spiral riblets, the uppermost one somewhat narrower, crossed by axial riblets 

 and nodulous in the crossing points; interstices between the tubercles smooth, 

 (or nearly so), and shining. Axial, riblets 15 in the third and fourth, 21 in the 

 penultimate whorl. Last whorl with a smooth basal keel beneath the 3 rows 

 of tubercles; base beneath this peripheral keel flattened and smooth, only with 

 growth striae. Aperture ovate-rhomboid, outer lip thin; columella short, straight; 

 canal oblique, short, about half the height of the aperture. Dimensions: h. 6,8, 

 br. 1,7, h. of aperture 1,2 mm. 



Masatierra, 30 — 40 m, sand with Corallina, V* 1917, 2 sps. 



On account of its smooth apical whorls this species is a true Cerithiopsis 

 (cf. Bartsch 1911'^), most closely related, as it seems, to T. gloi'iosa Bartsch 

 from California; the latter has, however, a more pronounced sculpture, especially 

 its basal keel is stronger, the base is concave and the canal is much wider. 



* The West American MoUusks of the Genus Triphoris. Proc. U. S. Nat. Mus. Vol. 35. 



* The Recent and Fossil MoUusks of the Genus Cerithiopsis from the West Coast of 

 America. Proc. U. S. Nat. Mus. Vol. 40. 



