20 Messrs. G. S. Brady and D. Robertson on the 
a laminated angular projection anteriorly (fig. 7 c), poste- 
riorly PY a strong rectangularly produced flange (fig. 7 d, 
fig. 5 d, and fig. 9d), from which projects a single sharply 
cut tooth, the flange itself being continued round the poste- 
rior margin of the valve (fig. 9 e); on the left valve by a 
deep sulcus behind, and a shallower one in front (fig. 6 f, 9). 
Except in front and at the supero-posteal angle, the margins 
of the valves are incurved considerably, so that the actual 
contact-margins embrace a much smaller area than that of 
the entire ee the right valve is larger than the left. 
Animal unkno 
Metacypris ce nov.sp. (Pl. VI. figs. 1-9.) 
Carapace excessively tumid and depressed: seen from the 
ds subovate or subrhomboidal, highest in the middle; 
height equal to more than half the length : anterior extre- 
mity well rounded, posterior obscurely angular: superior 
margin gently arched, produced at its posterior extremity 
into an angular process, corresponding in position to the 
aa hinge-joint; inferior margin distinctly convex, 
urving upwards behind, in front rather deeply and abruptly 
sinuated at its junction with the anterior margin. on 
m above, the outline is heart-shaped, pointed in ia 
posteris extremity broadly rounded and indented at the 
ume of the two valves; greatest width situated behind 
e middle, much greater than the height, and equal to 
bunt five-sixths of the length; the lateral m margins are 
boldly curved and somewhat sinuous in the anterior part of 
their course; end view subreniform, depressed; sides ex- 
cessively cony superior margin arched and slightly in- 
dented 1n the erige pom deeply sinuated in ihe middle, 
where, however, it is encroached on by the downwardly 
roduced anterior margin. Surface of the valves ey 
set with small rounded impressions, which are arrange 
longitudinal rows, running on the ventral surface into ide 
rupted furrows; ventral surface deeply and broadly sulcate 
along the greater ‘par of the median line. Colour brownish 
yellow. Length s inch. 
Hab. Rivers Nene, dm and Scheldt, Wroxham and Barton 
Broads, and Breydon Water. Scarce in all these localities. 
We much regret that we have been unable to find a trace of 
the animal structure of this remarkable ies, all our speci- 
mens being merely empty shells, the abnormal external cha- 
racters of which leave no doubt as to the propriety of establish- 
ing for it a new genus; but it is not so clear whether it ought 
to be placed amongst the Cypride or the Cytheride. 
