Cretaceous Gastropoda, and Pelecypoda from Zululand. 39 
Observations. — The material on which this new species is based 
includes two specimens with united and closed valves exhibiting 
most of the umbonal half of the shell, but considerably wanting in 
the ventral region : these occur in the soft reddish-brown marly 
matrix of the Manuan Creek district. Another, and the largest 
example, represents a left valve attached by its internal surface to 
the usual brownish-grey limestone rock of the same region ; it is 
imperfect antero-ventrally and the umbonal area is missing, other- 
wise the principal costae are well exposed. Beside these are two 
further fragments of a right and left valve showiug costal and 
umbonal characters, of similar lithological appearance and which 
were obtained from the same locality. 
This Trigonia belongs to Agassiz's group of the Scabrge,''' which 
includes Parkinson's aliformis ("Organic Eemains," 1811, vol. 3, 
pi. 12, fig. 9, p. 176), to which it is apparently closely related. It 
differs chiefly in the character of the costae, which are more numerous, 
especially on the umbonal area, as well as being of less delicate 
structure, being formed of coarser and wider annulations : the 
dividing furrows are not so deeply sculptured, giving a less elevation 
to the costse. Through imperfect preservation none of the finer ribs 
which should follow the earlier and stouter costae can be seen ; these 
in the true aliformis form numerous, equidistant, almost perpendicular 
ridges parallel to each other. 
Again, the African shell shows a more depressed surface at the 
anterior end or junction line of the valves, and there is little or 
no evidence of the marked depression which extends from the 
umbonal area down the posterior face of the valve to the postero- 
ventral region, as may be observed in all examples of the true 
aliformis. 
The new species, moreover, need not be confused with T. tuher- 
culifera of Stoliczka (Mem. Geol. Surv. India, Pal. Indica, 
1871, pi. 15, figs. 10-12, p. 315), from the Trichinopoly group of 
Southern India — a form which is of more quadrate contour, being 
considerably less excavated at the posterior margin, and possessing 
longer and narrower costae made up of segments of nearly one 
uniform size. In similar details the species from Zululand may be 
said to differ from T. ventricosa of Krauss, a species characterising 
the Lower Cretaceous (Neocomian) deposits of the Uitenhage dis- 
trict of South Africa (Nova Act. Acad. Cces. Leop.-Car., 1847, 
vol. 22, pi. 49, fig. 2, p. 456), which besides is of less anterior eleva- 
t 
* Agassiz, L. — Memoire sur les Trigonies. Etudes Critiques sur les Mollusques 
Fossiles [NeuchatelJ, 1840, p. 56. 
