MUSEUM OF COMPARATIVE ZOOLOGY. 67 



in size, and are strongly appressed against their predecessors, thus making the 

 line of the suture irregular ; whorls nine instead of twelve ; the body whorl 

 is quite different in sliape and sculpture ; the nodules, of which there are on the 

 last whorl only eleven instead of fourteen, instead of becoming obsolete on the 

 latter half of the whorl, are produced in the form of stout, strong ribs over 

 the periphery, when these suddenly cease and the anterior part of the whorl 

 is as it were constricted, instead of gradually tapering to the canal, so that the 

 latter is much more clearly differentiated from the rest of the aperture than is 

 usual in this genus ; there is no spiral sculpture, even on the canal where 

 traces are usually perceptible ; notch as usual ; a thin callus on the pillar ris- 

 ing into a sort of lamina at its outer edge forms a rather deep groove along 

 the columella, which last is attenuated anteriorly. Lon. of shell, 10.0 ; of 

 last whorl, 5.0 ; of aperture, 3.75 ; of canal, 1.5. Max. lat. of sheD, 3.0; of 

 aperture, 1.5 mm. Defl. about 22°. 



Station 21, 287 fms. 



Belonging to the same group as the last, but sufficiently distinguished 

 from it. 



P. (Drillia) Havanensis n. s. 



Shell somewhat variable, small, white, the first six whorls rather slender, 

 giving a subcylindrical apprarance, the latter whorls, if any, enlarging more 

 rapidly ; whorls about eight, of which about two are nuclear ; nucleus large, 

 white, smooth, unsculptured, forming for the shell a rather blunt button-like 

 apex ; succeeding whorls marked by a transverse sculpture of twelve to (on 

 the last turn) eighteen narrow, oblique, llexuous ribs, which begin as little 

 sharp nodules at the suture, are evanescent over the notch-band, thence con- 

 tinue to the next suture, or in the last whorl become evanescent at its anterior 

 third ; these ribs are crossed by a variable number of rather sharp revolving 

 threads, with wider interspaces, usually three or four in number (on the older 

 whorls) to sixteen (on the last whorl), beginning just in advance of the band ; 

 the first two are most prominent, and angulate the riblets where they cross 

 them, producing little raised points ; the succeeding threads are a little en- 

 larged where they cross the ribs, but do not form points, and are as usual 

 closer together on the anterior part of the canal ; on the band is no sculpture 

 except the lines of growth and an occasional faint indication of revolving 

 striae ; the number of riblets and of threads with their respective sharpness 

 and the prominence of the nodules are somewhat variable ; the band is some- 

 what excavated, tending to give a turreted appearance in old shells ; notch 

 broad, not deep ; outer lip thin, produced forward ; pillar straight, anteriorly 

 attenuated, with very little callus ; lines of growth well marked all over the 

 shell. Lon. of shell, 9.0 ; of' last whorl, 5.0 ; of aperture, 3.75. Max. lat, 

 of shell, 2.5 to 3.0 ; of aperture, I.O mm. Defl. 24° to 27°. 



Station 16, 262 fms. Station 19, 310 fms. Sigsbee, off Havana, 450 fms. 

 Yucatan Strait, 640 fms. 



