52 



BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



ceratum ceratum in the greater number of its early riblets, a shorter 

 stouter apex, and a more rapidly increasing diameter. The yellow 

 color seems to be more constant and vivid. It occupies an inter- 

 mediate position between D. ceratum ceratum and D. taphrium, though 

 quite distinct from both. 



The following are the museum collection records: 



1 Type. 

 DENTALIUM (ANTALIS) CERATUM TENAX, new subspecies. 



Plate 7, fig. 3. 



The shell differs only from the typical subspecies in that it is less 

 awl-shaped and more regularly curving; it is also rather more slender. 

 The color is less yellow in all the National Museum specimens, but 

 these have likely faded, as the material is old or poor. Almost com- 

 plete tips show a smooth nuclear portion, with 9 primary riblets 

 quickly increased to 12 or 14. All other sculptural features, includ- 

 ing the delicate intercostal network, are as in D. c. ceratum and D. c. 

 jiavum.. No apical notch is observable. 



The type, Cat. No. 95331 (a), U.S.N.M., measures— length, 19 mm.; 

 diameter, 1.75 mm. It is from Barbados, 76 fathoms, taken by the 

 BlaTce at United States Coast Survey Station 272, bottom of coral and 

 broken shell, with a temperature of 64.75° F. 



Other lots in the museum collection are from Barbados, in 100 

 fathoms. Cat. No. 95330, U.S.N.M., taken by the Hassler in 1871, 

 Barbados, in 33 fathoms; Cat. No. 314898, U. S. N.M., dredged by the 

 State University of Iowa Expedition Station 51; Barbados, in 70 

 fathoms, Cat. No. 314899, U.S.N.M., dredged by the State University 

 of Iowa Expedition Station 79. 



This is a geographic race of D. ceratum, occupying the extreme 

 southern limit of the range of that species. It is of the D. c. jiavum 

 type of ribbing, but smaller and more slender than that Floridian 

 subspecies. 



