72 BULLETIN 111, UNITED STATES NATIONAL MUSEUM. 



species belonii;in<^ properly to a shallower zone than that of 640 

 fathoms and normally possessed of a lateral apical slit. Until more 

 material is at hand Doctor Ball's species had best not be disturbed. 

 Doctor Dall has himself su«;<2;ested that so small and sharp a shell 

 might easily be caught in the meshes of the Blake's dredge net and 

 remain some time before finally being dislodged and washed into 

 the sieves. The following are the essentials of the description: 



The shell is small, thin, slightly curved, rather rapidly enlarging 

 with round section. The color is a translucent white, with opaque 

 white wavy lines encircling the shell, with zigzag markings and 

 producing an effect suggestive of moire antique silk. The sculpture 

 is of fine sharp close-set longitudinal grooves with narrower spaces 

 between — 36 in the middle and about 50 at the oral end. The aper- 

 tures are simple and featureless. 



The type, Cat. No. 203191, U.S.N.M., is a juvenile shell and unique 

 specimen and measures — length, 13 mm.; diameter, 1.2 mm. It 

 was dredged by the Blake, station not given, in 640 fathoms, oft' 

 Yucatan Bank. 



DENTALIUM (GRAPTACME) CALAMUS Dall. 



Plate 12, figs, 7, 8. 



1889. Dentaliwm calamus Dall, Bull. Mus. Comp. Zool., vol. 18, p. 421. 



1889. Dentalium calamus Dall, Bull. 37, U. S. Nat. Mus., p. 76. 



1892. Dentalium calamus Dall, Trans. Wagner Free Inst. Phila., vol. 3, pt. 2, 



p. 440. 

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



vol. 16, p. 97, pi. 16, figs. 55-59. 

 1903. Dentalium calamus Dall, Bull. 37, U. S. Nat. Mus., p. 76. 



The shell is slender, slightly curved, evenly and regularly increasing 

 in diameter from a rather blunt posterior end. The color is a tians- 

 ucent white, surface rather polished and vitreous in the anterior 

 portion. It is longitudinaPy grooved for the greater part of its 

 adult length with uniform regular lines, about 16 to the millimeter, 

 all rather abruptly temiinating and leaving the balance of the shell 

 smooth. The relative portions of scidptured and smooth surface 

 are somewhat variable, depending upon the amount of tip lost and age 

 of specimens. The posterior aperture is fiUed with a slit plug, 

 obliqely planed down on the convex side and therefore showing more 

 of the slit at the dorsal side. The apical plug is polished and seems 

 to form an integral part of the original shell, and not to be a casual 

 eature like the projecting tube so frequently seen in certain other 

 >pecies heretofore considered. The phallic appearance presented 

 by this slit plug is very striking and is unknown in any other species 

 from the faunal areas under consideration. Specimens measure: 



Length, 19.5 mm.; diameter, 1.25 mm.; arc, 1.25 (type). 



Length, 26 mm.; diameter, 2.1 mm.; arc, 1.5 (Cape Cajon, Cuba). 



Length, 24.5 mm.; diameter 1.75 mm.; arc, 1.25 (Porto Rico). 



