Nelso'ii on Tertiary Mollusca of Peru. 19') 



others. Base marked by six revolving lines. Fii-st narrow, separated 

 by deeply marked sutures. The next four form a series, narrowing 

 toward the interior, or umbilical region. The last, forming the wall 

 of the umbilicus, is broad and deeply notched Umbilicus widely 

 open. Three specimens, only, of this species have been found, all 

 slightly worn ; it is therefore impossible to state the superficial mark- 

 ings of the upper whorls. The species, however, appears to have 

 been notched transversely. Length 13 "8 millim. ; breadth 25 '2 

 millim. This species resembles S. grannlatum Lam., but that species 

 has seven lines on the base of the body whorl, instead of six as in 

 our species. 



Polinices subangulata, sp. nov. 



Plate VI, figures 4, 12, 13. 

 Shell varies from obliquely oval to sixb-globular, moderately heavy 

 and ventricose ; spire short and pointed ; whorls from six to seven, 

 convex ; body whorl large, nearly seven-eighths the length of the 

 shell, convex, slightly produced anteriorly, broadest about one-fourth 

 from top. From this point the whorl slopes, becoming very much flat- 

 tened and presenting a marked angular appearance. Surface marked 

 by distinct but irregular lines of growth. Sutures quite indistinct, 

 except when the epidenuis is slightly worn ofi". Apertui-e semi-lunar, 

 half as "svide as long, broadest a little below the middle. Outer lip 

 sharp and thin. Columellar lip covered by a very thick callus, which 

 rises into a more or less prominent ridge at the broadest part of the 

 shell. Umbilicus small ; in most specimens reduced to a mere chink 

 by the callus, which is prolonged below. Young, medium sized, 

 and full grown specimens give the following measurements : 



First, Length, 12-6 millim. Breadth, 9--4 millim. 



Second, " 28-2 " 22-2 



Third, " 47-4 " 39-2 



This is the most common species in the collection. In manner of 

 growth it resembles P. uher Val. sp., and is as variable as that species. 

 Young specimens of the two might easily be confounded. The young 

 are obliquely-oval ; by growth the body whorl becomes ventricose, 

 and the flattening of the upper part becomes more distinct and 

 prominent. The umbilicus also varies greatly. In some specimens 

 it is open and almost circular in outline, while in others it is almost 

 completely closed by a thick covering of callus. All full grown 

 specimens, hence, may easily be distinguished from any species with 

 which they might be confounded, by the short spire, the flattening or 

 angularity of the body whorl, and the small umbilicus. 



