24 DENTALIUM. 



iii, p. 103, pi. 224, f. 34 (1860); Conch. Icon., xviii, pi. 4, f. 23 

 (1872).— Brazier, Proc. Linn. Soc. N. S. Wales, ii, p. 56 (1877). 



Brazier writes : This species is six-ribbed near the apex, finely 

 striated below, as Mr. Sowerby expresses it. The specimens before 

 me have very fine, thread-like ribs; the number of ribs in all are 

 from 24 to 25, and at or near the apex 6. Shell thin, white, slightly 

 arched. 



There can be no reasonable doubt that " W. Columbia " cited by 

 Sowerby as a locality for this species, refers to specimens of D. oer- 

 stedii Morch. We have unfortunately no Oriental examples for 

 comparison with the West American species, and published descrip- 

 tions are insuflScieut ; but while the forms from opposite sides of the 

 Pacific may be identical, it is at least unlikely that they are. Des- 

 hayes was ignorant of the locality of his species, but he was 

 well supplied with East Indian material and had very little from 

 the Panamic Province, so it is somewhat likely that his types were 

 from the former region. Fig. 47 is a copy of Deshayes original fig- 

 ure. 



D. OERSTEDii Morch. PI. 10, figs. 60, 61, 62, 63, 64. 



Shell not much curved, decidedly tapering, rather solid, white. 

 Sculpture : hexagonal at and near the apex, with a narrow, raised 

 riblet at each angle, the intervals flat ; a short distance from apex 

 each face is divided by a riblet which soon attains the size of the 

 six primary ribs, and the tube becomes circular in section. Some- 

 what further on, each interval on the convex and lateral faces of the 

 shell bears a (tertiary) riblet, and still later these appear in the in- 

 tervals on the concave side, so that the number of riblets at the 

 middle of the shell is 12 (usually with some small threads also), and 

 at the aperture it varies from 21 (or sometimes as few as 17) to 24, 

 according to the age, and individual variation in development of 

 tertiary riblets on the concave face. Near the aperture the riblets 

 become rather low and wide, and are somewhat unequal. Growth 

 striae fine and inconspicuous, but occasionally there are low, varici- 

 forra rings on most specimens. 



Aperture slightly oblique, circular ; apex small, with circular ori- 

 fice without slit or notch of any kind. 



Length 39'5, diam. of aperture 3*5, of apex 1 mill. 



Length 37, diam. of aperture 3'2, of apex 0*9 mill. 



