1917.] NATURAL SCIENCES OF PHILADELPHIA. 171 



Strombus dominator n. sp. 



Slrombus gigas Linn., Gabb, Tr. Am. Philos. Soc, XV, p. 234. 



A species related to S. costatus {accipitri7ius) . Spire not very 

 high, the whorls having rounded tubercles on the periphery, and 

 spiral striae. The last whorl has a strong, rounded keel at the 

 shoulder, a stout, triangular tubercle in the middle of the back, 

 preceded by another on the side. There is an inferior series of small 

 tubercles, and on the latter part of the whorl, some low, coarse 

 spiral ridges. The lip spreads broadly and is much thickened 

 within. Posteriorly it extends above the apex. The throat is smooth. 



Length 88, diam. 75 mm. Length of aperture (measured from 

 end of canal to upper end of the lip) 97 mm. 



The type is an almost perfect but dwarf specimen. Several 

 fragmentary specimens are much larger, the best one about 15 cm. 

 long. The outer lip of another indicates a length of perhaps 20 cm. 

 It was apparently the mere size, rather than any close correspondence 

 of form or sculpture, which determined Gabb's reference of the form 

 to S. gigas. 



It is related to S. costatus and S. goliath, the spire being much like 

 the latter, which however, has the outer lip far more broadly expand- 

 ing, and the upper margin quite different. In S. costatus the lip 

 falls short of the height of the spire, but in S. dominator it rises 

 above the apex. 



Type No. 2579. 



Potamides gastrodon n. sp. 



The shell is rather short, conic, the whorls closely and regularly 

 sculptured with axial riblets crossed by three spiral cords, forming 

 small tubercles at the intersections. There .are a few inconspicuous 

 varices. Last whorl rises at the aperture, and has a prominent, 

 rounded varix on the left side; the cavity of the whorl at this place 

 having three well developed and a minute fourth tooth within the 

 outer wall, a fold on the parietal wall near the posterior angle, and 

 a plait on the columella. Last half of the last whorl is broken away. 

 As broken, the type measures: 



Length 22.5, diam. 11 mm. 



The type and three other broken specimens are No. 2599, A. N. S. P. 



Turritella sulcigyrata n. sp. 



Turritella planigijrata Guppy, Gabb, Tr. Am. Philos. Soc, XV, 1873, p. 240. 

 Not of Guppy. 



This species is closely related to T. gatimensis Conrad, but differs 

 by being constantly less excavated along the suture, though there is a 



