156 JURASSIC BIVALVIA AND GASTROPODA 



Remarks. The specimen now recorded is a large internal mould, 153 mm. high. 

 Its apical whorls are broken away, but the original height of its spire may be esti- 

 mated as 60 mm. The maximum diameter of the last whorl is about 130 mm. 

 The last whorl has a rounded-off shoulder bearing large blunt tubercles, about nine 

 in number, and above the shoulder is a sutural ramp of steadily increasing breadth 

 which eventually forms an angle of about 45 ° with the axis of the shell. The 

 tubercles and ramp are not seen on the mould of the earliest preserved whorls. The 

 outer face of the last whorl is of feeble convexity and more or less vertical, its outline 

 merging in a broad curve into that of the base, which is strongly excavated at the 

 beginning of the short neck of the specimen. It is improbable that an umbilicus 

 was present in the original shell. 



Schlosser (1881) placed Natica} subnodosa Roemer (1836 : 157, pi. 10, fig. 10) in 

 the synonymy of Purpuroidea gigas but did not adopt the earlier of the two specific 

 names. Brosamlen (1909) accepted this synonymy and adopted Roemer's name. 

 Examination of Roemer's figure of N.} subnodosa, however, raises considerable doubt 

 as to whether this represents a Purpuroidea at all. It illustrates a specimen with a 

 wide, flat sutural ledge, separated by a sharp, obscurely nodose angulation from the 

 vertical outer face of the whorl. No difference in the thickness of the wall of the 

 shell would produce a difference in the form of the internal mould comparable to 

 that between Roemer's figure and the illustrations of P. gigas given by Thurmann & 

 Etallon and by Schlosser. Moreover, I have recently had occasion to study a speci- 

 men from the Jurassic of Tunisia resembling Roemer's figure of Natica} subnodosa. 

 The specimen in question recalls the Hettangian species Ampullaria carinata Ter- 

 quem, which Cossmann (19136 : 174, pi. 9, figs. 14-17) has included in the genus 

 Tretospira Koken. It may, therefore, be suggested that Roemer's figure represents 

 a specimen belonging to that genus. Unfortunately, no specimens from northern 

 Germany of the species which Brauns records as Purpurina subnodosa (Roemer) and 

 states is characteristic of the Kimmeridgian are available to me, but it is to be sus- 

 pected that its identification with Roemer's species is incorrect. Brauns states that 

 specimens of the species reach a height of 180 mm. and a diameter of 150 mm. The 

 specimen from East Africa now recorded agrees quite well with the illustrations of 

 P. gigas given by the authors cited, but it seems desirable to qualify its specific 

 determination. 



Superfamily CERITHIACEA 

 Family PROCERITHIIDAE 



Genus PROCERITHIUM Cossmann 1902 

 Subgenus RHABDOCOLPUS Cossmann 1906 



Procerithium (Rhabdocolpus) mandawaense sp. nov. 



PI. 27, figs, ga, b, 10a, b, 11a, b, 12a, b 



Diagnosis. Shell of medium size for the subgenus (height of largest specimens, 

 when complete, c. 8 mm.) ; spire angle varying from about i5°-20°. Protoconch 



