CYTHERE. 173 
indentations visible, which give it a kind of wrinkled ap- 
pearance at that part. 
Hab. — Devonshire, W. C. Williamson, Esq.* Tenby, 
T. Rupert Jones, Esq. 
11. Cythere acuta. Tab. XXI, fig. 5. 
Shell oval, convex, acute at both extremities, which are 
nearly of equal size, of a pale, horny hue, smooth, glaucous, 
transparent ; upper margin considerably arched and 
rounded, the inferior one slightly so. In shape it some- 
what resembles a grain of oats. 
Hab. — Arran, in sand ; W. C. Williamson, Esq. 
12. Cythere pellucida. Tab. XXI, fig. 7. 
Shell oblong, reniform, narrow; both extremities rounded 
and nearly of the same size with each other ; pellucid, and 
of a white colour. The surface at first appears smooth 
and shining, but when examined with the microscope it 
is seen to be minutely dotted or punctated. 
Hab. — ^Boston, in ^and ; W. C. Williamson, Esq. 
13. Cythere impressa. Tab. XXI, fig. 9. 
Shell oval, very convex, of much the same size at both 
extremities. The surface of the shell is covered with im- 
pressed punctations, and the colour is of a dull blackish 
hue. The substance is of considerable thickness. 
Hab. — Torquay, in sand ; W. C. Williamson, Esq. 
14. Cythere quadridentata. Tab. XXI, fig. 2. 
Shell oval oblong, narrower at one extremity than the 
other ; the longer extremity (the posterior) rounded and 
slightly crenulated or toothed ; the narrower extremity 
(anterior) produced and terminating in four distinct 
* I am glad of this opportunity of acknowledging the kind and liberal 
manner in which Mr. Williamson has placed his specimens of Ostracoda in 
my hands for description. 
