Cretaceous Gastropoda, and Pelecypoda from Zululand. 37 
by numerous fine concentric striations and the more distant growth- 
lines. 
Dimensions (left valves). — 
Adult, Medium. 
Length 35 25 mm. 
Height 35 25 „ 
Diameter 15 9 
Observations. — The distioguishing character of the species is its 
ornamentation, the valves being covered with extremely fine and 
close radial costse of almost microscopical size, although coarser in 
the adult shell, forming colonies of equal width (less apparent on the 
lateral regions), each composed of about six costae, marked off by a 
pair of lateral ribs slightly more prominent than the others. In 
contour this shell resembles Pectunculus suhlcBvis of J. de C. 
Sowerby (Mineral Conchology, 1824, vol. 5, pi. 472, fig. 4, p. 112) 
from the Albian rocks of Blackdown, but in that species the radial 
costse are much wider, fewer, and of one order only, without any 
attempt at a zonal arrangement. 
In a similar way the present species differs from Forbes's P. 
suhauricidatus, from the Southern Indian (Pondicherry) Cretaceous 
{Trans. Geol. Soc, Londoji, 1846, Ser. 2, vol. 7, pi. 17, fig. 13), a 
species which Mr. Griesbach regarded as being related to his Natal 
species P. africanus [Quart. Journ. Geol. Soc, 1871, vol. 27, pi. 3, 
fig. 8, p. 66), described as possessing a " finely and radiately striated 
surface." 
Stoliczka's (Cretaceous Pelecypoda Southern India, Pal. Indica, 
1871, pi. 17, figs. 31, 32, p. 349) conception of Forbes' species 
is very unlike the type in general outline, but, strange to say, 
it agrees perfectly well with the contour of the present species, 
especially the younger valves, although the absence of any mention 
in the description of a zonal ornamentation is insufficient evidence 
for bracketing the African shell with the Indian form. 
Three of the medium-sized specimens (Manuan Creek district) 
are in a light-coloured limestone, the only right valve exhibiting 
some details of the hinge area. Another example (False Bay) of 
similar dimensions is of reddish-brown colour and quite isolated from 
the matrix ; it shows internal features but has a much eroded outer 
surface which obscures the ornamentation. The largest or adult valve 
(False Bay) is also isolated and of similar colour to the last referred 
to. It has a considerably fractured margin and a broken umbo, but 
in other respects the characters are well seen. The radial costae, on 
account of age, are somewhat coarser than in the smaller valves, 
and the posterior side is accentuated by an obliquely median furrow 
