36 
Transactions of the Boyal Society of South Africa. 
ventral region ; an obtuse, sloping carina extends from the umbo 
to the postero-ventral angle ; strong concentric periodical growth - 
lines ornament the lower half of the shell, at the margins of which 
occur obscure and nearly obsolete radial striations ; the surface 
between the umbo and the first growth-line is comparatively smooth. 
Dimensions (left valve). — 
Length 50 mm. 
Height 32 „ 
Diameter 20 ,, 
The worn character of this valve renders its relationships somewhat 
difficult to understand. It bears, however, some resemblance to 
Gucull(Ba rugosa of Holzapfel {PalcEontographica, 1889, vol. 35, pi. 22, 
fig. 1, p. 208) from the " Aachener Kreide " of Germany, the age of 
which is recognised as Lower Senonian or Emscherian. The shell 
possesses a similar straight ventral margin which is nearly parallel 
with the hinge-line, and from what can be seen of the dentition it 
seems to agree very closely with this European species. From 
T, ligeriensis it differs in its rather more abrupt and deeper posterior 
side. 
Locality. — Tributaries of the Manuan Creek. 
Family GLYCYMEEID^. 
Genus GLYCYMEEIS, Da Costa, 1778. 
Historia Naturalis Testaceorum Britannise, or, The British Conch - 
ology, 1778, p. 168. 
Synonyms — Axincea, Poli, 1795, and Pectunculus, Lamarck, 1799. 
Glycymeeis gkiesbachi, sp. nov. 
Plate HI., figs. 13-17. 
Description. — Shell convex, thick, sub-globose, nearly equilateral, 
sub-circular, length and height equal ; umbones rounded, incurved, 
almost mesial ; central region elevated, lateral areas deep and 
oblique ; anterior and ventral margins rounded, posterior region 
depressed, sub-angulate, grooved obliquely and medianly from the 
umbo (in the adult), and terminating with a marginal notch ; interior 
well excavated, round, with denticulated margin ; hinge area wide, 
sub-arcuate, with numerous divergent ligamental furrows, from 4-6 
elongate lateral teeth, the centrals being thick and distant ; orna- 
mentation exhibiting numerous, small, closely-set, rounded, radial 
costae forming equal groups of about six each, divided by lateral ribs 
of rather more prominence than the others ; radial sculpture crossed 
