MUSEUM OF COMPARATIVE ZOOLOGY. 85 



closed, reflected and rather short. Lon. of shell, 8.25 ; of last whorl, 2.0 ; 

 of aperture, 1.0. Max lat. of shell, 1.75 ; of nucleus, 0.5 mm. 



Yucatan Strait, 640 fms. Oft' Cape San Antonio, 640 fnis. Station 2, 805 

 fms. 



Without careful study the dift'erences between the forms of this group are 

 hardly noticeable. When examined under a high power it is soon found that 

 species which to the naked eye appear very similar or hardly distinguishable 

 are really characterized by quite a difterent method in their sculpture, though 

 the general result may be not very dissimilar in its salient features. The tu- 

 bercles of one are due to grooves cutting transverse riblets; of another, to spiral 

 ridges rising to nodules on the riblets ; of a third, to rows of nodules side by 

 side without spiral or transverse sculpture of any kind. This and the following 

 forms have been separated after several days' close study from an assembly 

 which the first examination had almost decided to place in the category under 

 one specific name. However, there are distinct definable dift'erences between 

 them, and the fact that the microscope is required to perceive these differences 

 should have no effect on our estimate of their systematic value. 



Triforis intermedius n. s. 



Shell, elongated, slender, acute, yellowish white, of about twenty-three 

 whorls ; nucleus missing in the specimens at hand ; spiral sculpture consist- 

 ing of two principal rows of rounded tubercles, with spirally confluent bases, 

 which are conspicuous from the beginning to the end of the spire ; if there is 

 any difference in size, the anterior row is slightly the larger ; there are about 

 eighteen of these tubercles on the last turn ; the posterior row lies close to and 

 somewhat appressed upon the suture ; midway between these is a smaller 

 spiral riblet, which rises into narrow elongated waves, or tuberculations, in 

 harniony with the others ; at the base of the whorl is a simple riblet very 

 slightly or not at all waved, and nowhere rising into tubercles ; these spiral 

 series are about equidistant, but the space between the anterior row of tubercles 

 and the basal riblet is more deeply excavated than the others ; base somewhat 

 flattened, conical, with an outer strong spiral ridge and two or three inner 

 fainter ones ; the transverse sculpture consists solely of the lines of growth, 

 which are conspicuous only on the base ; the tubercles, however, are arranged 

 so as to appear as if placed obliquely from right to left across the whorls, so 

 that on the length of the spire the transverse row makes nearly one revolu- 

 tion around the shell ; suture inconspicuous ; pillar short, stout, strongly re- 

 curved, with a thick and projecting callus ; anterior and posterior canals open 

 in the specimens examined ; outer lip produced anteriorly, very oblique, form- 

 ing a narrow aperture ; adult shell with the outline of the spire slightly 

 convex. 



Lon. of shell, 11.0 ; of last whorl, 2.25 ; of aperture, 1.5. Max. lat. of 

 shell, 1.75 mm. 



Station 2, 805 fms. 



