14 R. BULLEN NEWTON on 



numerous among recent examples of Rostellaria, although never developed in the 

 young state. The specimens are associated with Serpula tubes, which accounts 

 for certain small perforations observed in the test structure. 



OCCURRENCE. Cuttings Nos. 10, 12, 15. 

 COLLECTORS. Sir F. Lugard ; Mr. Kitson. 



Rostellaria unidigitata, sp. nov. 

 PLATE 4, figs. 3-7. 



DESCRIPTION. Shell robust, pyramidial above, oblong below, depresso- 

 convex ; body- whorl excavated at suture, obtusely margined, compresso-convex, 

 oblong, length exceeding that of the spire, canaliculated anteriorly and in rear ; 

 spire with 7 or 8 high and laterally depressed whorls, suture deep, nuclear whorls 

 smooth and obtusely apexed ; surface with strong spiral bands divided by longi- 

 tudinally striated grooves, earlier whorls, excluding the nuclear whorls, furnished 

 with numerous vertical plications, and obscure varices, body-whorl more or less 

 smooth, finely and microscopically striated in both directions in nearly half its 

 length, whilst the base is strongly and spirally ornamented ; aperture obliquely 

 elliptical, widely notched below and narrowly canaliculated at each end, the 

 posterior canal is directed backwards from the front along the sutural platform ; 

 labrum smooth within, border posteriorly excavated and outwardly curved below, 

 thick, with wide reflective lip, which forms a single spinose digitation in front, 

 afterwards surrounding the notch, and similarly the inner side of the narrow, 

 curved, anterior canal ; columella smooth, excavated, covered with a strong 

 callosity which is elevated, thick and much enamelled posteriorly where it forms 

 the inner boundary of the canal, which thins out at the angle and extends along 

 the sutural cavity of the body-whorl, besides forming part of the recurved 

 posterior canal. 



DIMENSIONS. 



Adult. Young. 



Alt. ... ... 50 ... 32 (from apex to end of anterior canal). 



Lat 24 ... 14 (from apex to digitation). 



REMARKS. This shell differs from R. bidigitata in the unidigitate character 

 of the labrum, extensive body-whorl, the recurvation of the posterior canal, and 

 the distribution of the callus over nearly half the basal surface of the penultimate 



