BYTHOCYPRIS BROWNEI. 13 



3. Bythootpris silioula (Jones). Plate II, fig. 64, and Plate III, figs. 27 — 30. 



Baibdia silicula, Jones. Monogr. Entom. Cret., 184-9, p. 27, pi. vi, figs. 20 a — c, 



and B. angusta (partim), Jones (not Miinster), ibid., 

 fig. 1 8 



Fig. 64 (left valve, outside). Length '805 ; lieight '417 mm. 



Fig. 27 (left valve, inside). „ 77; „ -417; tliickness '33 mm. 



Fig. 30 (left valve, female ?). „ '75; ,, '4 mm. 



Left valve subovate, obliquely rounded in front, and obliquely subacute behind ; 

 boldly arched on the dorsal, and nearly straight on the ventral border. Edge 

 view of the valves, if united, long-acute-oval ; end view subacute-oval. 



Near to BytJiocypris Beussiana, but more nearly oval, being much higher and 

 more fully arched in the middle third. 



Fig. 30 represents the external features of a left valve from the Chalk of Kent; 

 the interior and outlines were roughly given in figs. 20 a — c (figs. 27 — 29 in PI. 

 Ill) from the Charing Detritus. PI. II, fig. 64 (fig. 18 d), is also a left valve 

 (from the Gault of Folkestone), matching fig. 20 a, though not so full at the 

 dorsal margins as fig. 30. 



Localities. — Chalk, Kent, Keady Hill (Londonderry) ; Chalh-rock, near Luton ; 

 Detritus, Charing; Gault, Folkestone. 



3*. Btthocypris silicula, var. minor, nov. Plate III, figs. 40, 41. 



Length "7 ; height "325; thickness '3 mm. 



The left valve figured as above mentioned has much less height (from ventral 

 to dorsal border) than PI. Ill, figs. 27 and 30, and PI. II, fig. 64, the back being 

 less boldly arched. Otherwise the outlines are much alike ; and the difi'erence 

 may be varietal, if not merely sexual. 



Locality. — One specimen from the Chalk-rock oi Dunstable. 



4. Bythoctpeis Brownei, sp. nov. Plate III, figs. 38, 39, and 42, 43. 



Fig. 38. Length '8 ; height '4 ; thickness "3 mm. 

 Fig. 42. „ -7; „ -35; „ -3 „ 



Two subreniform or bean-shaped left-hand valves, from the Chalk-rock of 

 Dunstable, have much in common as to their outhne and contour. 



