234 INVERTEBRATA OF MASSACHUSETTS. 



tionate length of this is greater, the thick, white callus indicates a 

 mature shell, and the dark portion of the upper whorls is at the 

 upper instead of at the lower portion of the whorl, as in N. heros, and 

 the umbilicus is proportionally smaller instead of larger, as is the case 

 in young shells. Besides, I have never seen a large shell in the lo- 

 calities where this species is abundant. The largest specimen I have 

 seen, which I could distinctly refer to this species, is less than an inch 

 in length. It is evidently analogous to N. canrena of Europe. 



It varies in marking greatly. Some specimens are of a pale yellow- 

 color, and destitute of marking ; on some, the spots blend so as to 

 present alternate bands of light and dark color ; again, some of the 

 series are blended, and some are not. The spots may be square, 

 oblong, or crescentic, and are usually oblique. The ivory-white callus 

 seems to be the most constant character. 



NATICA IMMACULA'TA. 



Shell small, sub-ovate, solid, bluish-white) spotless, glossy, um- 

 bilicus free . 



FIGURE 168. 



State Coll., No. 46. Soc. Cab., No. 951. 



Natica immaculkta, TOTTEN ; Sillimaris Journ., xxviii. 351, f. 6. 



Shell sub-ovate, extremities rather pointed, solid, milk-white, 

 and glossy when deprived of its thin, greenish-yellow epidermis ; 

 spotless, lines of growth faintly perceptible ; whorls about five, 

 the spire very short and pointed, and the suture not impressed ; 

 the lower whorl convex and rounded, prolonged at the base ; 

 aperture narrow oval, rather acutely curved at base ; outer lip 

 sharp, inner margin coated with ivory-white callus, not modifying 

 the umbilicus, but extending along the margin to its posterior limit ; 

 at the posterior angle of the aperture it is much thickened, and, 

 running along under the junction of the whorls, causes a white 

 spiral line to appear externally, just below the suture ; the region 

 before the umbilicus too, is very white ; umbilicus rounded and 

 deep ; operculum horny. Length J| inch, breadth 5 \ inch. 



First found by Colonel Totten in Newport harbour, and after- 

 wards in Provincetown harbour. It is found plentifully in the 

 stomachs of fishes taken in Massachusetts Bay. 



I know of no species resembling this, except it be N. A'nglica, of 



