EAST AMERICAN SCAPHOPOD MOLLUSKS. 29 



DENTALIUM (DENTALIUM) TEXASIANUM CESTUM. new subspecies. 



Plate 2, figs. 1, 4, 8. 



The shell is characterized by an abundant intercalation of rather 

 heavy cord-like riblets, which assume equal importance with the 

 primaries and in the mature and senile stages obscure the hexagonal 

 section of the shell. 



The type, Cat. No. 159503 (a), U.S.N.M., is from Pass Cabello, 

 Texas. It measures 18 mm. in length, with a diameter of 2 mm., 

 and was collected by J. D. Mitchell. It is the only specimen of the 

 lot and is without station data. It is probably a beach specimen 

 and of very shallow depth range. 



DENTALIUM (DENTALIUM) TEXASIANUM RIOENSE, new subspecies. 



Plate 2, figs. 2, 8. 



The shell is characterized by its rounded smooth intercostal spaces 

 and by little or no intercalation of secondary ribs. The primary six 

 rod-like ribs are even more slender and delicate than in the sub- 

 species D. t. texasianum. 



The type, Cat. No. 96114, U.S.N.M., measures: Length, 17.2 mm.; 

 diameter, 1.5 mm. It is from east of Rio de Janeiro, at U. wS. B. F. 

 station 2762, in 59 fathoms, blue mud, bottom temperature 57.1° F., 

 from a lot of 12 specimens. 



There are also four specimens from the same original lot. Cat. 

 No. 203143, U.S.N.M.; also one specimen. Cat. No. 150784, U.S.N.M., 

 from San Sebastian, Brazil, presented by Ihering without additional 

 data. 



DENTALIUM (DENTALIUM) GOULDII Dall. 



1889. Dentalium gouldii Dall, Bull. Mus. Gomp. Zool., vol. 18, ])t. 2, p. 424, in 



part. 

 1889. Dentalium gouldii Dall, Proc. U. S. Nat. Mus., vol. 12, p. 295, in part. 

 1889. Dentalium gouldii Dall, Bull. 37, U. S. Nat. Mus., p. 76, in part. 



1896. Dentalium gouldii, Guppy and Dall, Proc. U. S. Nat. Mus., vol. 19, p. :^25, 



in part. 



1897. Dentalium (Dentalium,) gouldii, Pilsbry and Sharp, Tryon's Man. Conch., 



vol. 17, p. 20, not pi. 7, fig. 14, in part. 



The shell is hexagonal, slightly curved, regularly tapering and 

 solid; white, vitreous, polished, and shining. It is six-angled at the 

 apex, the angles becoming narrow, pinched-up, rod-like ribs, sepa- 

 rated by broad fiat spaces. Between these spaces are microscopi- 

 cally fine engraved longitudinal lines, more or less apparent, about 

 16 in the space of 1 mm., extending from the apex over about one- 

 fourth the length of the shell and then terminating quite suddenly; 

 the intercostal surfaces thereafter are smooth and polished with some 

 transverse growth line scratches. The primary ribs become less 



