FROM TANGANYIKA AND KENYA 153 



Diagnosis. Shell of medium size for the genus (original height of holotype c. 12 

 mm.), phasianelliform, height of aperture about two-fifths of that of shell ; spire 

 angle about 35 °. Protoconch unknown (broken off in holotype). Spire whorls 

 rather high, moderately convex, abutting simply at the sutures ; last whorl broadly 

 convex at periphery. Base evenly convex in outline, not much extended ; no 

 clearly open umbilicus is seen, but a small cleft in the base of the holotype may be 

 the opening of a very narrow one. Aperture ovate, angular posteriorly, not oblique. 

 Columellar lip straight and vertical although not much extended, slightly undercut 

 by a well-marked sinus which separates it from the basal margin of the aperture. 

 Outer lip orthocline ; details of parietal region not well seen in available specimen. 

 Growth-lines obscure. 



Holotype. No. GG.10281. The only specimen. 



Locality and horizon. z\ miles N.N.W. of Kidugallo, Tanganyika ; Bajocian. 



Remarks. The apertural characters of this species and of the one described next 

 agree with those of members of the family Coelostylinidae rather than with those of 

 the pseudomelaniid subgenus Oonia, which they greatly resemble in the general 

 morphology of the shell. The only Bajocian and at the same time the geologically 

 youngest representative of the family hitherto recognized, is Coelostylina brasili 

 Cossmann (19136 : 217, pi. 8, figs. 58, 59), from France. This form is more than 

 twice the height of the species now described and has a less distinct sinus at the foot 

 of its columella. Cossmann pointed out that certain species from the Bajocian of 

 England described by Hudleston (1891 : 251-255, pi. 19, figs, n-15) under the 

 generic name Phasianella might well belong to Coelostylina. Specimens identified 

 by him (1891, pi. 19, figs. 11a, b, 14b) as Phasianella elegans Morris & Lycett (a 

 Bathonian Oonia) are very similar to the African species now described. 



Coelostylina mandawaensis sp. nov. 

 PL 25, figs. 4a, b, 5a, b, 6a, b, ya, b 



Diagnosis. Shell of medium size for the genus (height of largest specimen 13 

 mm.), ovate-conical, aperture occupying rather less than one-half of total height. 

 Protoconch minute, dome-like. Spire slightly cyrtoconoid, acute, consisting of 

 feebly to moderately convex whorls abutting simply at the sutures ; last whorl 

 broadly rounded at periphery. Base extended, evenly convex in outline ; no clearly 

 open umbilicus is seen, but a small median cleft in the base may be the opening of a 

 very narrow umbilicus. Aperture much higher than broad. Columellar lip ex- 

 tended, straight and vertical or leaning slightly to the left adapically and joining the 

 basal margin in a very abrupt curve, the junction forming a slight beak-like pro- 

 tuberance. Margin of columellar lip narrowly reflected, partly covering umbilical 

 cleft and continued across parietal region by margin of a thin inductura which passes 

 beneath the outer lip. Growth-lines prominent on last whorl, prosocline near the 

 suture, orthocline below. 



Holotype and paratypes. Holotype, no. GG. 10283. Numerous paratypes, 

 including nos. GG. 10284-86. 



