26 THE ENTOMOSTRACA. OF 



long, delicate, and well-defined, the median bar and furrow elongate and simple, but 

 the anterior and posterior isolated teeth on the right valve are knurled or crenulated, 

 their surfaces presenting 4 — 5 minute rounded knobs or denticles, which fit crenulate 

 furrows on the other valve. 



Dorsal aspect irregularly ovate, with the ends produced ; end-view triangular, with 

 the lateral lines slightly curved. 



The specimens which I here refer to C. triangularis, Reuss, — agreeing with that 

 species in all essential particulars, — occurred not unfrequently in the London Clay, 

 from the excavations made for the Great Northern Railway in the Copenhagen Fields, 

 north of London, and were obtained by Mr. J. Purdue, to whom I am indebted for the 

 majority of my specimens from the London Clay. Reuss describes his specimens as 

 occurring in the Cretaceous deposits at Basdorf, near Kropelin, in Mecklenburg; 

 several of the microzoa of these beds, as Reuss well remarks, have a tertiary aspect. 



No. 4. Cythere Wetherellii, Jones. Plate IV, fig. 15; PI. VI, figs. 16 a — 16 d. 

 Cythere Wetherelli, Jones. Quart. Journ. Geol. Soc, x, p. 161, t. 3, fig. 9. 



INCH. 



Length, -^ Middle Eocene : Isle of Wight. 



Carapace irregularly ovate ; contracted posteriorly ; convex and somewhat flattened 

 towards the ventral portion; suddenly inturned and flattened along the ventral border; 

 bearing a subtriangular impression at about the middle of the dorsal portion of each 

 valve ; surface of the valves ornamented by a delicate reticulation, the meshes of which 

 are formed by slightly raised anastomosing borders ; reticulation fading away towards 

 the dorsal margin : hinge delicate, presenting a modification of the hind and front teeth 

 of the right valve, which are finely knurled, and connected by a continued fine knurling 

 of the edge of the valve, whilst the median bar and furrow are obsolete. 



Dorsal aspect narrow-oblong, with the ends angular and produced ; end-view almost 

 quadrangular, somewhat pentagonal. 



Cythere Wetherellii is not uncommon in the Middle Eocene Sands of Colwell Bay, 

 Isle of Wight, and also in an Oyster-band 1 of this series at the same locality. One 



1 Some years since a handful of this clay with remains of oysters was given to me as having heen 

 brought from Woolwich ; and the species of Entomostraca which I had obtained from it (viz., C. Wetherellii, 

 C. plicata, and C. angulatopora) were in consequence enumerated in the ' Quart. Journ. Geol. Soc.,' vol. x. 

 p. 160, as belonging to the Woolwich series. Since then I have satisfied myself of the incorrectness of the 

 stated locality of this clay. The above-mentioned species must therefore be regarded as belonging to the 

 Middle, and not the Lower, Eocene. 



