GEOGRAPHIC DISTRIBUTION. XX111 



Indo-Pacific Province East Indies, Philippine Islands, Singapore 

 to N. Papua. 



About 20 species of Dentalium and two Cadulus are reported 

 from definite localities in the " East Indies," nearly all being shallow 

 water species, the deep water forms being still unknown. No doubt 

 many other species recorded from China and Japan, Torres Strait, 

 and the Indian Ocean, also occur here. The specialty of this tract 

 is the group of green colored species. 

 D. elephantinum. D. variabile. 



D. formosum. D. belcheri. 



D. aprinum. D. acutissimum, 1,070 fms. 



D. interstriatum. D. bisinuatum. 



D. javanum. D. longitrorsum. 



D. letsonse. D. eburneum. 



D. hexagonum. D. philippinarum. 



D. bisexangulatum. D. subrectum. 



D. pseudosexagonum. Cadulus gadus, p. 186. 



D. dispar. C. singaporensis, p. 195. 



D. quadrapicale. 



Key to species of Dentalium. 



a. Shell ribbed, decidedly colored, generally green. Group of D. 



elephantinum, p. 1 ; and of D. aprinum, p. 3. 

 a'. Shell ribbed, white or whitish, not green. 



b. Square, with four right angles or keels at apex, becoming 

 rounded at aperture. 



c. The four primary ribs bifid or trifid, dispar, p. 32. 

 c'. Primary ribs simple; surface costulate, about 36 

 riblets at aperture, which is very oblique, 



quadrapicale, p. 34. 

 6'. Hexagonal or 6-ribbed at apex. 



c. 6-ribbed throughout, intervals smooth or with 

 several strise toward aperture; length 55 mill., 12- 

 14 times the diam. hexagonum, p. 18. 



c'. Each interval divided and subdivided by succes- 

 sively arising riblets, pseudosexagonum, p. 23. 

 b". 10-13 ribs, or more. 



c. 11-13 ribs throughout, the ribs not dotted ; a weak 

 thread in intervals or none, bisexangulatum, p. 15. 

 c'. Ribs dotted or articulated, gray and white, 



variabile, belcheri, p. 60. 



