337 



quadrate or tiattish witli three prominent ribs, moderately 

 impressed suture, the medial ones usually granulose. Base 

 flattened, ornamented with many unequal-sized spiral threads, 

 which are crossed by very tine radial striae. Aperture subquad- 

 rate, margins united by a somewhat tliick callus, which extends 

 over much of the base ; columella arched, regularly curving to 

 the rounded basal lip ; outer lip somewhat flatly compressed, 

 deeply and broadly sinuated. 



The ornament on the whorls varies much in diflerent speci- 

 mens, as well as in different parts of the same shell. The 

 medium prominent rib is generally granulose ; the posterior rib 

 is bisulcated, or not infrequently replaced by two or three strong 

 threads ; the interspaces between the ribs and adjacent to the 

 sutures are ornamented with a few sjDiral threads crossed by 

 curved lines of growth. On the anterior whorls of large 

 examples there are about eight unequalled-sized spiral ribs— the 

 posterior rib on the earlier whorls has developed into three 

 prominent ribs, and one or more of the intermediate threads have 

 become conspicuous, whilst the granulations of the medium rib 

 have disappeared. 



The posterior six whorls or so have occasionally all the ribs 

 granulose, thus resembling T. Sturtii ; but at this early stage 

 T. Aiding (p does not jDossess intermediate ribs. 



Dimensions. — Length, 36 ; breadth, 10'5 ; depth and width of 

 sinus, 3. 



Localities. — Eocene: Argillaceous limestone and associated 

 clays at Blanche Point, Aldinga Bay (very abundant), and Ade- 

 laide-bore ! ; also in the " Turritella limestone" about Ardrossan, 

 Yorke Peninsula (J. G. 0. Tepper ! ). 



In outline, general shape of whorls, and deep sinus, this fossil 

 species has an analogue in T. ritncinnto, Watson, " Challenger" 

 Gasteropoda, p. 475, t. 30, fig. 3 ; compared with actual speci- 

 mens of which, the fossil is conspicuously distinguished by curved 

 columella (not straight in the axis, and effusively dilated at the 

 front), and tricarinate whorls. 



4. Turritella Warburtoni, Ttn.-Wood.s. Pi. viii., fig. 2. 



Shell small, narrowly pyramidal ; whorls 15, in a length of 

 9 -5 mm. ; apex of two and a-half smooth turns, the tip subglobu- 

 lose, the next turn narrow and convex : ordinary whorls concave, 

 separated by a narrow deeply impressed suture, roundly elevated 

 at the posterior suture, more angulated and elevated at the 

 anterior suture ; posterior to which and near to is a more acute 

 but less stout keel ; the two anterior ribs more or less granulose; 

 each of the interspaces between the keels with two or three fine 

 threads of varying size. Growth-lines hardly discernible, slightly 



