160 JURASSIC BIVALVIA AND GASTROPODA 



Genus CRYPT A ULAX Tate 1869 



Cryptaulax bussagensis (Cossmann) 

 PL 27, figs. la, b 



1843 

 1851 

 1863 

 1885 

 1899 



Cerithium pentagonum d'Archiac : 384, pi. 31, fig. 6 (non Bronn, 1831). 

 Cerithium pentagonum d'Archiac ; Morris & Lycett : 39, pi. 9, fig. 22. 

 Cerithium ? negleclum Lycett : 92, pi. 44, fig. 21 (non Deshayes, 1833). 

 Cerithium pentagonum d'Archiac ; Cossmann : 103. 

 Cerithium bussagense Cossmann : 135. 

 19136. Cryptaulax pentagonum (d'Archiac) ; Cossmann : 104, pi. 4, figs. 100-102. 



Material. One specimen (no. GG. 10464). 



Locality and horizon. 2 miles W. of Tengeni (village on Pangani river), in 

 Mbuzi Mkubwa stream, Tanganyika ; Bathonian (?). 



Remarks. This specimen, a small cerithiiform shell lacking its apical whorls 

 but originally about 16 mm. high, has flat whorls bearing five rounded transverse 

 costae with intervals of about the same width. The costae are in almost uninterrup- 

 ted alignment on successive whorls and are very slightly prosocline. The specimen 

 agrees well with examples of the species from the Great Oolite of England. As 

 Bronn's Cerithium pentagonum cannot be dismissed as a nomen nudum it is necessary 

 to find a replacement for the same name proposed by d'Archiac for the Bathonian 

 species. The name Cerithium bussagense was proposed by Cossmann as a substitute 

 name for the similarly homonymous C. neglectum Lycett, founded on a specimen 

 consisting merely of the earlier whorls of d'Archiac's C. pentagonum, and it is now 

 adopted for this species. 



Superfamily STROMBACEA 



Family APORRHAIDAE Philippi 1853 



Genus PIETTEIA Cossmann 1904 



Pietteia stockleyi sp. nov. 



PL 27, figs, ja, b, 8a, b, 14a, b, c 



Specific name. After Mr. G. M. Stockley, formerly Director of the Geological 

 Survey of Tanganyika. 



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

 7-9 mm.), rather slender, mean spire angle about 20 °. Protoconch elevated, rather 

 mammilliform, of two smooth whorls. Later whorls about 5|, rather high in pro- 

 portion to their diameter, with a moderately wide sutural ramp which forms an angle 

 of about 45 with the axis of the shell and an almost flat outer face, which is vertical 

 or even inclined inward abapically on the last whorl, and is separated from the feebly 

 excavated, well extended neck of the shell by an obtuse angulation. Dominant 

 ornament consisting of spiral threads ; three principal threads, with a secondary 

 thread varying in strength intercalated in each interval on the later whorls, are 

 present both on the outer face and on the ramp, and further threads, irregularly 



