292 Annals of the South African Museum. 



culatus, Forbes," from the Ariyalur Group, but is relatively shorter, 

 less rounded in outline, with the hinge-line more strongly curved 

 and the lateral teeth more oblique. The ornamentation also appears 

 to be somewhat different. 



Bemarks.—¥oYty specimens of this species have been seen. The 

 type is in the Hambui'g Museum. 



Family TEIGONIID^. 



Genus TEIGONIA, Bruguiere. 



Trigonia Shepstonei, Griesbach. 



Plate XXXV., figs. 1, 2. 



1871. Tri(jo7iia Sliepstonei, Griesbach, Q.J.G.S., xxvii., p. 66, 

 pi. iii., fig. 11. 



Description. — Shell subtrigonal, very inequilateral, produced 

 posteriorly ; length greater than height. Valves inflated anteriorly, 

 gradually compressed posteriorly. Anterior margin rounded, form- 

 ing a regular curve which passes gradually into the ventral margin. 

 The posterior part of the ventral margin slopes upwards to join 

 the short, oblique posterior margin. Postero-dorsal margin long, 

 concave. Umbones of moderate size, incurved, situated at a 

 distance from the anterior end equal to about a quarter of the 

 entire length of the shell. Area moderately large, flattened, some- 

 what truncated posteriorly, with a longitudinal furrow near the 

 middle. There is a narrow carina near the umbo, but it becomes 

 indistinct posteriorly. Escutcheon large, excavated. 



Ornamentation consists of from 17 to 19 strong, slightly curved 

 costae, which are separated by rounded interspaces of much greater 

 breadth than themselves. The costae bear short, stout, erect spines. 

 Fine ridges cross both costae and interspaces. Near the umbo the 

 costae are concentric, but in the middle of the valve they run in 

 a dorso-ventral direction. They cut the anterior margin obHquely, 

 and are nearly perpendicular to the middle part of the ventral 

 margin ; towards the posterior extremity they slope posteriorly. On 

 the anterior part of the area there are transverse costellae ; in passing 

 posteriorly the costellae become more oblique and less distinct. The 



* Trans. Geol. Soc, ser. 2, vol. vii. (1846), p. 150, pi. xvii., tig. 13. Stoliczka, 

 Cret. Fauna S. India, vol. iii. (1871), p. .349, pi. xvii., figs. 31, 32. 



