VO l889 n ] PROCEEDINGS OF THE NATIONAL MUSEUM. 317 



tic of deep water species of many diverse groups; the typical Cono- 

 mitra has a small but also rather bulbous nucleus. It is possible that 

 the whiteness of this shell is due to its dead condition, but it has the 

 unmistakable abyssal facies and is probably colorless iu life. Only two 

 dead specimens, one a mere fragment, were obtained. 



Family FASCIOLARIID^. 



Genus FASCIOLARIA Lamarck. 



Subgenus MESORHYTIS Meek. 



Mesorhytis costatus sp. nov. 



Plate v, Fig. 5. 



Shell small, thin, slender, the axis slightly bent, of a pale cinereous or 

 buff color, with six or seven whorls; nucleus large for the size of the 

 shell, rather inflated and loosely coiled, polished white; spiral sculp- 

 ture on the early whorls from four to six little-elevated flattish threads 

 with subequal interspaces; between the suture and the periphery on 

 the later whorls these spirals disappear but persist on the periphery and 

 between it and the succeeding suture or the end of the canal ; on the 

 last whorl these threads become faint or obsolete, but on the preceding 

 whorls do not enlarge in crossing the ribs; transverse sculpture on the 

 earlier (except the first two) whorls, of eight to eleven rather stout 

 narrow ribs or costse, extending from a little iu front of the suture over 

 the periphery, where they are strongest, to the uext suture, and over- 

 run but not nodulated by the spirals; on the last whorl the transverse 

 as well as the spiral sculpture becomes obsolete ; suture distinct, some- 

 what appressed ; whorls noderately rounded; canal slender, slightly 

 tortuous and distinctly recurved ; aperture elongate, pointed before 

 and behind, the canal distinct ; outer lip thin, simple, not internally 

 lirate; pillar slender, twisted, with a thin glaze; one shorter anterior 

 and two posterior strong transverse plaits. Maximum longitude of 

 shell, 14; maximum latitude of shell, 4 mm . 



Hab.— U. S. Fish Commission Station 2751, south of St. Kitts, West 

 Indies, in north latitude 16° 54' and west longitude 63° 12', in G87 fath- 

 oms, globigerina ooze ; bottom temperature 39°.9 F. 



This species, like M. MeeMi Dall, was taken without the soft parts. 

 It is a minute fusiform Fasciolaria with the transverse plaits of a Mitra. 

 In Ptychatr actus, which seems to be its northern representative, the 

 plaits resemble those of Fasciolaria and not those of Mitra. The group 

 was first differentiated by Meek as a Cretaceous fossil. Both the recent 

 species inhabit the deep waters of the Antilles. A fragment of still 

 another species, or a Cordicria, insufficient for description but evidently 

 new, was dredged in 49G fathoms, at Station 2750, near St. Bartholomew, 

 West Indies. 



