280 bulletin: museum of comparative zoology. 



shoulder, behind which it is slightly excavated ; this area is spirally sculptured 

 ■with numerous, very fiue, close-set threads, one of which, two-thirds of the way 

 to the keel, is more prominent than the others ; these are crossed by numerous 

 rather irregular low sharp ridges strongest near the keel, which they nodulate 

 more or less, especially on the earlier whorls, and, fading out toward the suture, 

 faintly reticulating the spirals; keel high, sharply compressed below, with a rounded 

 edge ; whorl in front of it spirally sculptured with numerous flat low ridges with 

 narrower channelled interspaces, the ridges crossed by fine sharp lines of growth 

 and occasional faint vertical folds, low and obsolete except near their beginning in 

 front of the keel ; body polished, with the sculpture erased ; outer lip angulated 

 and notched by the keel, thin, sharp, simple ; pillar short, white, with a faint brown 

 band around it ; the anterior portion acute, and obliquely truncate ; canal short, 

 slightly recurved. Lon. of (eroded) shell, 12.5 ; of last whorl, 11.0 ; of aperture, 

 9.0 ; max. diam., 7.7 mm. 



U. S. S. " Albatross," station 3393, Gulf of Panama, in 1020 fathoms, mud, 

 bottom temperature, 36°.8 F. U. S. N. Mus. 123,112. 



This is quite a peculiar shell, and looks more like one of the northern Belas 

 than any of the preceding species. 



Pleurotomella (Gymnobela) xylona Dall, n. ep. 



Plate 2, figure 3. 



Shell thin, white, elongate, subturrited, with eight whorls beside tiie (lost) 

 nucleus; suture distinct, deep, not channelled; whorl in front of it sloping flatly 

 to an angular shoulder, sculptured with three or four flattish spiral threads with 

 slightly wider interspaces separated from the keel at the shoulder by a channel 

 three times as wide as the others ; shoulder keel duplex, the posterior cord most 

 prominent, the anterior, closely adjacent, less so ; in front of these, extending to 

 the canal, is a series (five on the penult, eighteen on the last whorl) of similar but 

 less prominent, subequal, and subcquidistant cords, with numerous smaller inter- 

 calary threads, the interspaces wider than tlie primary cords ; from the shoulder to 

 the periphery on the last whorl are (on the type about fourteen) numerous obscure 

 narrow vertical riblets extending to but not over the base, but not nodulatiug 

 the superincumbent cords; there are also numerous very fine, slightly prominent 

 lines of growth which tend to roughen the spiral sculpture; aperture short, wide; 

 outer lip (defective) thin, simple; body wilh the sculpture erased, polished, milk- 

 white; pillar very short, gyrate, almost pervious; canal very short and wide. 

 Lon. of shell, 27; of last whorl, 16; of aperture, 12; max. diam. 12 mm. 



U. S. S. " Albatross," station 3413, near the Galapagos Islands, in 1360 

 fathoms, ooze, bottom temperature 36" F. U. S. N. Mus. 123,111. 



A form of problematical relations, perhaps least out of place here, until more 

 is known about it. 



