88 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



cular ; peristome double, the inner slightly exserted ; the outer expanded. 

 Operculum with subcentral nucleus, bearing many slender, retractively 

 curved riblets, extending from the inner edge outward and growing 

 weaker outwardly, vanishing before reaching the outer edge of the 

 chondroid basal plate. 



Type species: Orciittipoma orciitti, new species. 



KEY TO THE SPECIES OP ORCUTTIPOMA 



Outer peristome narrowly expanded orcutti 



Outer peristome broadly expanded rollei 



OB.CUTTIPOMA OBCITTTI, new species 



Plate 14, Figure 6 



Shell elongate-conic, unicolor or with a brown subperipheral band, 

 sometimes also indications of another band are present above the pe- 

 riphery. Nuclear whorls 2, decidedly inflated, strongly rounded, micro- 

 scopically granulose. Postnuclear whorls inflated, strongly rounded, and 

 marked by almost vertical sublamellar axial riblets, of which 6o are 

 present on the last turn in the type. These axial riblets may be straight, 

 slightly wavy, or even weakly scalloped. The spaces between the axial 

 riblets are marked by numerous microscopic, closely spaced spiral lines. 

 Suture very strongly constricted. Periphery well rounded. Base short, 

 openly umbilicated, and marked by the continuation of the axial ribs, 

 which extend upon the umbilical wall and the microscopic spiral stria- 

 tions referred to for the spire. The last whorl is solute for a fraction 

 of a turn. Aperture broadly oval ; peristome double, the outer nar- 

 rowly expanded, forming a slight auricle at the posterior angle and 

 marked by concentric lines; the inner slightly exserted and reflected. 

 Operculum as described for the genus. 



The type (U.S.N.M. No. 504001) was collected by Orcutt a little 

 north of Abricots. It is a complete specimen having y.y whorls and 

 measures : Height, 8.3 mm. ; greater diameter, 3.4 mm. ; lesser diameter, 

 3.0 mm. 



This species, unlike the others of the genus, always has the spire com- 

 plete. There is considerable variation in the strength of the waviness 

 and scalloping of the ribs as well as in the spiral lines. There is also 

 variation in the thickness of the spire, but I have been unable to connect 

 these differences with geographic distribution ; the same thing may occur 

 in a large gathering from any locality. There are 50 lots before me 

 collected by Mr. Henderson and myself or by Mr. Orcutt. Their dis- 

 tribution ranges from Abricots around the coast to Aquin Bay on the 

 south side. Orcutt also collected it on the lie a Vache, but even these 

 seem inseparable from those of the main island. 



U.S.N.M. No, 401648 contains 53 topotypes from the same source. 



U.S.N.M. No. 401667 contains 11 specimens collected by Orcutt on 

 the west bank of the Riviere Trou Sardines. 



