315 



DESCRIPTIONS OF NEW FOEMS OF MARGINELLID^ AND 

 PLEUROTOMID^. 



By E. R. Stkes, B.A. 



Read 12th May, 1905. 



PLATE XVII. 



The foiins now described have been received from various sources, the 

 majority having been kindly placed at my disposal by Mr. Sowerby 

 when he acquired Admiral Keppel's collection. I have taken the 

 opportunity of characterizing a form of Marginella from the "Porcu- 

 pine " Expedition, as it may be some little while ere I am able to deal 

 with this group. 



All the figured specimens are in my own collection. 



Marginella imperatrix, n.sp. PL XVII, Figs. 1, 2. 



Shell ovate-oblong, longitudinally costate, there being about 20 costfe 

 on the last whorl, polished, shining, yellowish-white, with blackish- 

 fuscous blotches and rows, both spiral and transverse, of black spots, 

 these latter varying in shape from rounded or square to oblong ; spire 

 elevated, conoid ; whorls b^, the protoconch being smooth and some- 

 what obtuse and of pale horn-colour, the later whorls moderately 

 convex ; aperture narrow, elongate, white within, columella almost 

 straight at the base, with four folds, the lower pair ascending and the 

 upper almost horizontal, these latter being (in the adult shell) provided 

 with indications of smaller folds supporting them below ; lip white, 

 much thickened, and lightly crenulate within, the black spots being 

 seen on and behind the outer margin. 



Long. 38 mm.; diam. max. 18 mm. 



Hah. — West Africa (Keppel). 



A near ally of the well-known M. pseudofaba, Sby. ; the present 

 species is, however, a trifle larger, and narrower in proportion to the 

 length, the spii'e being correspondingly a little more elongate ; the 

 columella is not so curved at the base, and the longitudinal costae are 

 more numerous, being on the last whorl in about the proportion of 

 twenty as compared with twelve, while they are finer and extended 

 over a larger portion of the shell. Young specimens of both species 

 have been figured for comparison (PL XYII, Figs. 2, 4). 



Marginella Keppelt, n.sp. PL XVII, Fig. 3. 



Shell ovate-oblong, smooth except for obsolete longitudinal costfe 

 which are inconspicuous and fairly numerous, polished, shining, 

 greenish- white, with numerous black spiral lines (two of which appear 

 on the upper whorls), and longitudinal black lines which are either 

 straight, zigzag, or united into blotches; spire moderately elevated, 

 conoid ; protoconch blunt ; whorls A\ to 5, plano-convex ; suture in- 

 conspicuous ; aperture rather narrow, white within ; columella four- 

 plaited, fairly straight at the base, the canal being tinged with black 



