160 Annals of the South African Museum. 



The anterior ribs are narrower and perhaps rather more pro- 

 minent than the posterior ribs. Delicate and fairly regular lines 

 of growth cross the surface of ribs and interspaces alike. The 

 surface of the shell, where well preserved, is seen to be covered 

 by very numerous and delicate, radially disposed lines of minute 

 granules. 



Dimensions. The anterior part of the specimen is hidden in the 

 matrix, but to judge from the course taken by the anterior growth- 

 lines, the length of the valve may be fairly accurately estimated as 

 22 mm. The umbo is situated at about one-third of the total length 

 from the anterior extremity, assuming that the above length-measure- 

 ment is correct. The height of the valve at the umbonal region is 

 13 mm. The height of the siphonal border is 8 mm. 



Occurrence. Collected by Mr. Eogers from the highest beds in 

 the kloof behind Colchester, Sunday's Eiver Valley (489g). 



Remarks. This is the first specimen of Goniomya recorded from 

 the Uitenhage Series. The condition of the single valve available 

 for comparison scarcely justifies a specific determination, and the 

 question of relationships cannot be usefully discussed without better 

 material for study but the specimen probably represents a new 

 species. 



It is interesting to find the genus Goniomya represented here, in 

 strata which yield the peculiar Trigonice of the group of T. vau 

 which so strongly simulate the genus Goniomya both in the 

 arrangement of the costate ornaments and in the general habit. 

 Though the specimen above described at once recalls these 

 Trigonice, it may be readily distinguished from them by the very 

 thin shell-wall and the presence of surface granulation, as well as 

 by the details of ornamentation. In Trigonia vau Sharpe and its 

 allies, the neanic stage is ornamented by concentric ribs passing 

 across the flank and area, and the inclination of the ribs with 

 resulting angular pattern is not produced until the early adult 

 stage. In this Goniomya, the costse formed an anterior and a pos- 

 terior series, steeply inclined, already in the neanic stage, at a very 

 much shorter distance from the umbonal apex than in the Trigonice, 

 mentioned. 



GENUS THRACIA W. E. Leach. 



THEACIA sp. 

 Plate VIII., fig. 5. 



A single specimen, which must be ascribed to this genus, is 

 scarcely so well preserved or so strongly characterised as to allow 



