28 DENTALIUM. 



[seabriusculis] ribs; the intervals concave, sculptured with very 

 minute transverse ribs. Apex entire, minute, somewhat campan- 

 ulate. Length 0'74, diam. 12 mill. (M. & R.}. 



Orange Bay, Patagonia. 



Another form of this species was collected by the U. S. Fish Com- 

 mission at Sta. 2777 and 2780 in 77^-369 fms., bottom temp. 36-46 

 Straits of Magellan. It has the riblets on the median portion of the 

 shell unequal, alternating, becoming subequal toward the aperture 

 where they are rounded and parted by narrow grooves, instead of 

 acute, with wider concave intervals as in the type. Length 57, diam. 

 4'5 mill. This form may be called var. MAGELLANICUM (pi. 12, figs. 

 95, 96, 97). In the specimen figured there are 12 or 13 riblets at 

 apex, 24 at aperture. Type no. 87561 U. S. Nat. Museum. 



D. SHOPLANDI Jousseaume. PI. 12, fig. 100. 



Shell large, but slightly curved, nearly straight, solid, slowly 

 tapering ; cream-white with gray- white ribs. Sculpture : near the 

 apex 17 subequal but unequally spaced, narrow, sharply defined riblets 

 very much narrower than the interspaces; these continue to the 

 aperture, increasing in size ; their number is early increased by the 

 intercalation of some interstitial threads, mainly on the concave side, 

 so that at the aperture there are 25 unequal, unevenly spaced ribs 

 and threads ; the whole surface densely and conspicuously striated 

 transversely, the striae unequal, like cords scattered among threads, 

 crenulating the riblets. Aperture oblique, subcircular, a trifle wider 

 than long, the peristome jagged from fracture. Apex large, the 

 orifice simply circular, without notch or slit. 



Length 78'5, diam. at aperture 10, at apex 3'2 mill. 



50 miles off Aden, in 678 fms. 



D. shoplandi Jouss., Bull. Soc. Philomath, de Paris (8), vi, p. 

 102 (1894). 



A large species, apparently without near allies. It is remarkable 

 for the prominence of the growth-striae, and the clearly carved ribs 

 of the surface. 



Figure and description are from a specimen in coll. U. S. National 

 Museum. Jousseaume's original diagnosis is as follows : 



Shell large, gray-white, cylindrical, slightly arcuate, longitudi- 

 nally costate, transversely densely lamellose-striate ; ribs 21, sub- 

 equal, separated by flat grooves. Length 75, diam. 11 mill. 



