230 BULLETIN 192, UNITED STATES NATIONAL MUSEUM 



OPISTHOSIPHON (OPISTHOSIPHON) TUBKENSIS, new species 



Plate Z7, Figure 2 



Shell elongate-ovate, small, pale yellowish, marked with inconspicuous 

 interrupted spiral bands of brown, of which four occur between the 

 summit and the suture and two on the base. Nuclear whorls decollated 

 in all our specimens. Postnuclear whorls inflated, strongly rounded, nar- 

 rowly shouldered at the summit, and marked by rather distantly spaced, 

 sublamellar axial riblets, of which 36 occur upon the first, 56 on the 

 second, and 60 on the last in the type. These riblets become expanded 

 into moderately large hollow cusps at the summit. The spiral sculpture 

 consists of rather strong threads, which are ill-defined on the first turn, 

 but 12 of them occur on the remaining whorls between the summit and 

 suture. These threads render the axial riblets sharply nodulose and some- 

 what wavy. Suture narrowly channeled. Periphery well rounded. Base 

 short, somewhat inflated, well rounded, openly umbilicated, and marked 

 by the continuation of the axial ribs and seven spiral threads. Eight ad- 

 ditional spiral threads are present within the umbilicus. Aperture very 

 broadly oval, almost subcircular; peristome double, the outer broadly, 

 flaringly expanded, more so on the inner lip than the outer and marked 

 by a series of concentric lines and forming a conspicuous auricle at the 

 posterior angle which is adnate to the breathing siphon ; inner peristome 

 exserted and slightly reflected. Operculum typically opisthosiphonid. 



The type (U.S.N.M. No. 355444) comes from the H, Prime Collec- 

 tion and was collected on Turks Island. It has a little more than 3 whorls 

 and measures: Length, 8.7 mm.; greater diameter, 5.3 mm.; lesser di- 

 ameter, 4.4 mm. 



U.S.N.M. No. 355445 contains 2 specimens from the same source. 



Five additional specimens (U.S.N.M. No. 57605), collected by Raw- 

 son, yield the following measurements : 



This species resembles most nearly O. (O.) vaughani, from which 

 the sharp nodulations will readily differentiate it. 



OPISTHOSIPHON (OPISTHOSIPHON) VAUGH.\NI, new species 



1905. Opisthosolen hiformis bahamensis Dall, The Bahama Islands, Geogr. Soc. 

 Baltimore, p. 42, in part. 



Shell elongate-conic, flesh-colored, with a yellowish tinge, usually 

 marked by interrupted spiral bands of brown. The elements composing 



