168 JURASSIC BIVALVIA AND GASTROPODA 



than one-half of total height. Protoconch conical, with minute apex. Spire acute, 

 conical, consisting of feebly to moderately convex, smooth whorls, abutting simply 

 at the sutures. Last whorl evenly and strongly convex at periphery, its outline 

 flattening out basally but not becoming definitely concave before reaching the aper- 

 ture. No distinct umbilicus. Aperture pyriform, peristome not continuous across 

 parietal region. Columellar lip thin, rather extended, straight or almost so, vertical 

 or leaning slightly to the left, and joining the basal margin in an even curve. Outer 

 lip defective or crushed in the available specimens, apparently almost orthocline, 

 although growth-lines are scarcely distinguishable on the surface of the shell. 



Holotype and paratypes. Holotype, no. GG.10302 ; several paratypes, in- 

 cluding no. GG. 10303. Ex B.P. Coll. 



Locality and horizon. Near site of Mandawa well no. i, Tanganyika ; Bajo- 

 cian (?). 



Remarks. This species resembles the type-species of Pictavia, Natica pictaviensis 

 d'Orbigny (1852 : 191, pi. 289, figs. 8-10), from the Bajocian of France, in the general 

 morphology of the shell, but its small size distinguishes it both from that species and 

 from other Middle Jurassic representatives of the genus that have been described 

 previously. 



(Superfamily uncertain) 



Family MATHILDIIDAE 



Genus PROMATHILDIA Andreae 1887 



Promathildia aff. opalini (Quenstedt) 

 PL 29, figs. 6a, b 



1832 

 1856 

 1882 

 1883 

 1884 

 1891 

 1891 

 1909 



Aff. Turritella elongata Zieten : 43, pi. 32, fig. 5 (non J. Sowerby, 1814). 



Aff. Turritella opalina Quenstedt : 326, pi. 44, fig. 15 (non Adams & Reeve 1850). 



Aff. Turritella opalini Quenstedt : 300, pi. 196, figs. 20, 21. 



Aff. Cerithium torulosi Quenstedt, pi. 205, fig. 53. 



Aff. Turritella (Mathilda) opalina Quenstedt var. canina Hudleston : 200, pi. 7, fig. 9. 



Aff. Turritella (Mathilda) opalina Quenstedt ; Hudleston : 231, pi. 17, figs. 3a, b. 



Aff. Turritella (Mathilda) opalina var. canina Hudleston ; Hudleston : 232, pi. 17, fig. 4. 



Aff. Turritella opalina Quenstedt : Brosamlen : 275, pi. 20, fig. 44 ; pi. 21, fig. 1. 



Material. One specimen (no. GG. 10270). 



Locality and horizon. Didimtu hill, 2 miles S. of Bur Mayo, N.E. Kenya ; 

 Upper Lias, Toarcian, Didimtu Beds. 



Remarks. The specimen, which is 13-5 mm. high, lacks the actual apex, but 

 consists of about 6| early whorls of an acute, turriculate shell. The whorls, which 

 are strongly and evenly convex, are mostly eroded, but the last one can be seen to be 

 ornamented with about 8 obscurely granose spiral cords. 



Hudleston (1891 : 231) suggested that Quenstedt's name Turritella opalina might 

 " be accepted as a generalized term for elongate Turritellae of Jurassic age possessed 

 of about six or seven spirals ", and mentioned that the spirals were slightly granula- 



