Cretaceous Gastropoda, and Pelecypoda from Zuhtland. 65 
ventral border ; posterior margin oblique, elongate, rounded at 
ventral extremity ; upper valve flat, slightly convex near umbo, and 
a trifle smaller than opposing valve ; lower valve moderately convex ; 
sculpture on both valves consisting of numerous convex, radial costso 
occasionally interrupted by concentric periodical growth-lines ; costae 
bifurcating about the middle of the valve, imbricated and furnished 
with small tubular spinose projections at the various margins of 
growth ; the costae are separated by shallow sulcations. 
Dimensions. — 
Length 19 mm. 
Height 19 „ 
Diameter 7 ,, 
Observations. — The above description is founded upon a small 
specimen with both valves standing slightly open, of which the 
umbones are not preserved. Although the ornamentation of the 
valves is on the same plan in each, yet the lower has longer and 
more developed tubular spines which extend occasionally beyond 
the margins, whilst the upper valve is comparatively smooth from 
the fact that the tubular terminations of the costae are shorter and 
do not overlap the border. The specimen shows affinities with 
Plicatula aspera-'' (J. de 0. Sowerby, Trans. Geol. Soc. London, 1832, 
ser, 2, vol. 3, pi. 38, fig. 7) from the Upper Cretaceous deposits of 
Gosau, Austria — a species which apparently differs by possessing a 
flat or slightly concave upper valve, as well as having less oblique 
sides and consequently a less triangulate contour, and in addition the 
costae, although as crowded, are not so straight as in the specimen 
now described. Slight resemblances are traceable with P. multi- 
costata of Forbes as emended by Stoliczka (Cretaceous Pelecypoda, 
Southern India, Pal. Indica, 1871, pi. 34, figs. 15-18, pi. 46, 
figs. 5, 6, p. 446) from the Trichinopoly group of Southern India, but 
the valves of the present shell have a more obliquely oval form and 
are ornamented with more regular and straighter costae. 
A number of Plicatulae are recorded from the Upper Cretaceous 
rocks of Northern Africa, especially by Coquand in connection with 
Algeria, Zittel and others in respect of Egypt, and Blanckenhorn 
* It may be here noted that Sowerby's Plicatula asi^era was based entirely upon 
a figure without description. In 1846 Orbigny (Pal. Fran^aise Terr. Cretaces 
Lamellibranchia, 1846, pi. 463, figs. 11, 12, p. 686) purported to describe and 
illustrate the same form as found in France, but, as pointed out by Stoliczka, 
" this can hardly be regarded as identical with the one from the Gosau " formation. 
The true interpretation of the old Sowerby figure is, however, to be found in Zittel's 
€xcelleat drawings and description of specimens found in the same beds of the 
Austrian Tyrol [Denkschr. k. Akad. Wiss. [Wien], 1866, vol. 25, pi. 19, fig. 1, 
p. 120). 
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