MUSEUM OF COMPARATIVE ZOOLOGY. 87 



twice as large as that of T. colon, smooth, inflated, rounded on top, larger than 

 the succeeding nuclear whorl, which has two inconspicuous narrow keels which 

 are wavy and almost tuherculate from the first, and pass imperceptibly into the 

 usual sculpture of the shell ; spiral sculpture of two rows of somewhat elongated 

 tubercles (about eighteen to the last turn), sometimes degenerating into a wavy 

 riblet ; these tubercles are arranged much as in T. colon, but are narrower in 

 a direction transverse to the whorl, with their transverse connections less 

 evident, the spiral ridge proportionately stronger, and the tubercles individu- 

 ally less conspicuous ; the two spiral rows of tubercles, especially in the an- 

 terior part of the shell, occupy the peripheral third of the visible part of the 

 whorl; * the anterior and posterior thirds are somewhat excavated toward the 

 suture, the shell being appressed and slightly raised on each side of the latter, 

 but without forming a regular band or riblet, unless in the very last whorl 

 where the raised edges are a little waved in sympathy with the tuberculation of 

 the periphery ; suture very distinct ; the excavation above referred to gives a 

 particularly rounded appearance to the whorls, resulting in a wholly different 

 aspect from that given by the subcylindrical T. colon, which has twenty-three 

 whorls in the same space as sixteen of T. ibex; base rounded with three Btrong 

 raised threads between the anterior tubercular spiral and the canal ; canal 

 short, a little recurved at the tip ; pillar with a strong callus ; posterior canal 

 and outer lip not completed in any of the specimens at hand, but the more 

 adult ones indicate a rather wide roundish mouth ; outlines of the spire a little 

 concave from the button-like nucleus. Lon. of shell, 11.0; of last whorl, 3.0; 

 of (immature) aperture, 1.5. Max. lat. of shell, 1.87 ; of nucleus, 0.5 mm. 



Off Cape San Antonio, 640 fms. Yucatan Straits, 640 fins. Sigsbee, off 

 Havana, 450 fms. 



This shell tapers more rapidly than T. colon, as will be seen by the measure- 

 ments, and differs in the other particulars mentioned from that species, which 

 appears to be its nearest ally. 



Cerithiopsis (?) Sigsbeana n. s. 



Shell long, slender, excepting the inflated apex acutely conical, sides recti- 

 linear, with about twenty-three whorls ; color, nucleus translucent, first three 

 or four whorls with a deep reddish brown tinge which gradually fades to waxen 

 white, tinged irregularly with faint brown or yellowish suffusion, in dead shells 

 pure white, polished and partly translucent ; nucleus inflated, vitriniform, Bel 

 on a little obliquely, projecting outward more than the two subsequent apical 

 whorls, smooth, but latterly faintly sculptured in transition toward the regular 

 BCulptuxe of the shell by faint posteriorly concave transverse undulations ; sub- 

 sequent spiral sculpture of three and afterward four spiral flattened Bquarish 

 ridges, the most prominent of which is the posterior, which is in front of and 

 covers the invisible suture ; before this are two equal and slightly but distinctly 

 smaller ones, and lastly at the anterior margin of the shell (except in the very 

 * Of courso, proportionately much more in tin earlier whorls. 



