126 BULLETIN 68, UNITED STATES NATIONAL MUSEUM. 



about two and one-half times as wide as the ribs, marked by a very- 

 broad, deep, peripheral pit and two less wide on the anterior third 

 between the sutures; the median third is marked by three moderately 

 broad pits, separated by slender lirations, the shoulder has a narrow 

 line immediately below the summit and three well incised lines anterior 

 to this, the anterior of which is less strongly developed than the other 

 two. The spaces between the second and third, and third and fourth, 

 posterior to the peripheral one, are wider than the rest. All the 

 raised areas between the pits are crossed by very fine spiral striations. 

 Periphery of the last whorl slightly angulated. Base short, well 

 rounded, marked by the feeble continuations of the axial ribs and ten 

 spiral striations, which decrease in size and spacing from the periphery 

 to the umbilicus. Aperture rhomboidal; posterior angle obtuse; 

 outer lip thin; columella slender, very oblique, and slightly re volute. 

 The type (Cat. no. 96806, U.S.N.M.) was dredged at U. S. Bureau 

 of Fisheries station 2799, in 30 fathoms, on green mud bottom in 

 Panama Bay. It has lost the nucleus and probably the first post- 

 nuclear turn. The nine remaining measure : Length 5.3 mm., diame- 

 ter 1.6 mm. Cat. no. 162694, U.S.N.M., contains three more speci- 

 mens from the same station. 



Subgenus PYRGISCTJLTJS Monterosato. 



Pyrgisculus Monterosato, Conch. Medit., 1884, p. 28. 



Turbonillas with turrited spire having the whorls decidedly con- 

 tracted at the suture, and tabulated at the summit, marked on the 

 spire and base by many well incised spiral lines. 



Type. — Melania scalaris Philippi. 



KEY TO THE SPECIES OF THE SUBGENUS PYRGISCULUS. 



Whorls shouldered. 



Shoulder strongly excavated. 



Axial ribs almost interrupted at the shoulder monilifera, p. 126. 



Axial ribs continuing strong to the summit cancellata, p. 127. 



Shoulder not excavated. 



Axial ribs 12-8 • festiva, p. 127. 



Axial ribs 16-20 eucosmia, p. 128. 



Whorls not shouldered. 



Spiral striations between the sutures 8 paucilirata, p. 129. 



Spiral striations between the sutures 15 swani, p. 129. 



TURBONILLA (PYRGISCULUS) MONILIFERA, new species. 

 Plate 12, fig. 15. 



Shell pupiform, bluish- wliite. (Nuclear whorls decollated.) Post- 

 nuclear whorls flattened in the middle, scarcely contracted at the 

 suture, with a strong shoulder that covers the posterior fourth 

 between the sutures, forming a decided angle at its termination. The 



