30 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



defined anteriorly, but the hexagonal section is usually preserved, 

 though not so distinctly at the aperture. There is no intercalation 

 of secondary ribs except in one form, later described. No apical 

 features are shown in any National Museum specimens. 



The type, Cat. No. 82997, U.S.N.M., measures: Length, 29 mm.; 

 diameter, 2.75 mm.; arc, 1 (tip gone); and is from 12 miles east of 

 Frying Pan Shoals in 12 fathoms. It was collected by Doctor Rush, 

 who has given no further data. 



Tiie glossy hyaline surface, the fine longitudinal engraved lines, 

 and the general faces of this shell separate it from D. texasianum. 

 It is apparently a moderate depth species. Tnree subspecies are 

 indicated by the National Museum material. 



Tiie very few records in the National Museum collection, which 

 are particularly referred to under the subspecific headings, indicate 

 this to be a species of wide Antillean and Gulf Stream range, but 

 not an abundant one at any known station. 



DENTALIUM (DENTALIUM) GOULDII GOULDII Dall. 



Plate 2, figs. 6, 7. 



This subspecies, answering the original description of Doctor Dall 

 for Dentalium gouldii, may be characterized by tlie well-marked 

 microscopic sculpture within the intercostal spaces of its shell; by 

 its straight outline, and the complete absence of any intercalation 

 of secondary ribs. Tiie intercostal sculpture, consisting of longi- 

 tudinal lines, is sufficiently marked to be visible to the unaided eye. 



The single specimen in the National Museum collection is the type 

 referred to in the description of D. gouldii, next preceding. As this 

 particular form of D. gouldii has not appeared at any of the many 

 Florida shallow dredging stations it is undoubtedly a form of narrow 

 geographical range and confined to the inner Gulf Stream edge off 

 the Carolinas and Georgia. 



DENTALIUM (DENTALIUM) GOULDH PORTORICENSE, new subspecies. 



Plate 2, fig. 5. 

 1901. Dentalium gouldii Dall and Simpson, U. S. Fish. Comm. Bull. 1, 1900, p. 

 455. 



The shell is hexagonal, thin but strong, vitreous, with a polished 

 surface; the ribs are narrow and rod-like, separating broad flat 

 spaces, which lack the clearly defined, very fine longitudinal lines of 

 D. g. gouldii, although in oblique light they may be detached by use 

 of a strong lens. Tiie ribs become less defined anteriorly, while the 

 intercostal spaces become convex, both finally merging in senile 

 specimens into a round cylinder, the merest traces of the ribs remain- 

 ing visible at the aperture. No intercalation of secondary ribs is 

 shown. The apical characters are uncertain. Tne curvature of tlie 

 shell is greater than in the ty[)ical subspecies and is uniform through- 

 out the entire length of an adult shell. 



