ball: mollusca and brachiopoda. 275 



MANGILIINAE. 



BORSOIVIA Bellardi, 1838. 

 Borsonia (Borsonella) dalli Arnold. 



Plate 13, flgure 9. 



Pleurotoma {Borsonia) dalli Arnold, Mem. Cal. Acad. Sci., 1903, 3, p. 201, pi. 6, 

 fig. 2. 



Pliocene and Pleistocene of San Pedro, Arnold. XJ. S. S. "Albatross," station 

 2839, in 414 fathoms, sand, bottom temperature 41°. 4 P., and 2918, iu 67 

 fathoms, sand, temperature 52°.4; off the edge of the Cortez Bank, N. Pacific 

 Ocean. U. S. N. Mus. 96,841 and 122,576. 



Borsonia (Borsonella) agassizii Dall, n sp. 



Plate 1, figure 5. 



Shell biconic, the aperture shorter than the spire, apex eroded but with six 

 remaining whorls, white and chalky under a pale greenish yellow periostracum ; 

 suture distinct, not appressed, the whorls sloping flatly to the periphery wiiich is 

 marked by a rounded keel with (on the last whorl fifteen) obscure elongated swell- 

 ings or uodulations ; the anal fasciole which is close to the suture is marked by 

 lines of growth concavely arcuate, crossed by half a dozen spiral incised lines in 

 the path of the sulcus ; below the keel are lines of growth, obscure traces 

 of spiral distant incised lines, and numerous irregularly impressed striae, wliich 

 are perhaps patliological ; base moderately convex ; outer lip thin, sharp, strongly 

 protractive below the keel, above the latter with a wide, shallow anal sulcus reach- 

 ing close to the suture ; body polished, niilkwhite ; pillar short, twisted, wliite, 

 with a well-marked spiral plait near its insertion; canal wide, short, distally 

 funicular, somewhat recurved. Lon. of shell (decollate), 23; of last whorl, 15; 

 of aperture, 11; max. diam. 11 mm. 



U. S. S. "Albatross," station 3361, Gulf of Panama, in 1471 fathoms, ooze, 

 bottom temperature 30°.6 F. U. S. N. Mus. 123,107. 



This species resembles B. dier/eusis Dall in outline, but is larger, has the carina 

 proportionately nearer the middle of the whorl, and the nodulation of the keel is 

 strongest on the last whorl ; while in dicgensis it is more marked on the earlier 

 whorls and is sometimes entirely obsolete on the later ones. The latter species 

 also has the vermicular impressed sculpture fiuer and much closer, tkough this 

 may be i)alhological. 



Borsonia (Borsonella) diegensis Dall, n. sp. 



Plate l.t, n«iire 11. 



Shell small, stout, solid, decollate, with a whitish substratum and strong oliva- 

 ceous periostracum ; the four remaining M'horls are closely coiled and have the 



