FROM TANGANYIKA AND KENYA 161 



spaced but alternating in strength more or less regularly, ornament the neck. In 

 addition, weak collabral ribs, most prominent at the ramp angle, are present except 

 on the last whorl, the number on the penultimate whorl being 10. On the last 

 whorl the ramp angle bears a short spine half a volution back from the outer lip. 

 Aperture narrow, not preserved intact in the available specimens. Outer lip thick- 

 ened, with a single short digitation at the position of the ramp angle. 



Holotype and paratypes. Holotype, no. GG.10359. Four paratypes, including 

 nos. GG. 10300-01. All ex B.P. Coll. 



Localities and horizon. Near site of Mandawa well no. i, Tanganyika (holo- 

 type). Mandawa well no. 6, from depths 46-48 feet, 58-60 feet and 60-62 feet. All 

 Bajocian (?). 



Remarks. Although the outer lip is imperfect even in the best-preserved speci- 

 men, there is little doubt that this species is a Pietteia related to P. hamus (Eudes- 

 Deslongchamps) (see Hudleston, 1888 : 113, pi. 4, figs, ba-d ; pi. 7, fig. 9) and P. 

 unicarinata (Hudleston) (1888 : 118, pi. 4, figs, i^a-c), both of which occur in the 

 Bajocian of England. It differs from these forms in details of ornament, and in P. 

 unicarinata the ramp angle bears two spines on the last whorl, respectively at one- 

 quarter and one-half of a volution back from the aperture. 



Pietteia mandawaensis sp. nov. 

 PI. 30, figs. 8a, b 



Diagnosis. Shell small (height of holotype, a specimen defective anteriorly, 8.0 

 mm.), spire slightly cyrtoconoid, its mean angle probably about 30 ° originally (but 

 affected by slight crushing in the available specimens). Protoconch bluntly conical, 

 of z\ smooth whorls. Later whorls about 6, of moderate height, the last three with a 

 fairly wide sutural ramp which forms an angle of about 45 ° with the axis of the shell, 

 and an almost flat outer face which is inclined inward abapically and on the last 

 whorl is separated from the feebly excavated neck of the shell by a well-marked, 

 obtuse angulation. Ornament consisting of spiral threads crossed by rounded 

 collabral ribs which are well marked on the earlier whorls but become obsolete on the 

 penultimate and last. Three spiral threads of primary strength are present on both 

 the outer face and the ramp, secondary threads of varying strength occupying their 

 intervals, and further threads ornament the neck. The number of collabral ribs on 

 the pre-penultimate whorl is about 12. On the last whorl a short spine is situated at 

 the ramp angle half a volution back from the outer lip. Aperture not preserved 

 intact. 



Holotype and paratypes. Holotype, no. GG. 10382. Three paratypes, nos. 

 GG.10383-85. 



Locality and horizon. Near site of Mandawa well no. 1 ; Bajocian (?). 



Remarks. This species resembles P. stockleyi, described above, in size and in the 

 nature of its ornament, but its whorls, including those of the protoconch, are much 

 lower in proportion to their diameter than in that species, and its collabral ribs are 



