BYTHOCYPRIS SIMULATA. 11 



This species is somewhat like Macrocypris decora, Brady, ' Trans. Zool. Soc.,' 

 vol. V, 1866, p. 866, pi. Ivii, fig. 13 ; and ' Challenger Report,' 1880, p. 44, 

 pi. i, fig. 3, and pi. vi, fig. 8 : but it is shorter, much more deeply incurved at the 

 antero-ventral region, and more acute posteriorly. It may rather be said to have 

 the characters of our M. Wrightii (see p. 10) in a much less elongated frame. 



Localities. — From the Chalk of Kent and the Detritus at Charing, Kent. 



4. Maoeootpeis oonoinna, sp. nov. Plate II, figs. 66, 67. 



Length '95 ; height '85 ; thickness "3 mm. 



Valves rather long, subtriangular, nearly straight on the ventral, and neatly 

 arched on the dorsal margin ; rounded in front, narrower and obliquely rounded 

 behind. Surface gently convex. Edge view of the united valves long-acute- 

 oval. End view oval. 



Locality. — Two specimens from the Chalk-rocJc of Dunstable ; one of them 

 (broken and not figured) is rather larger than the other (fig. 67), rather rounder 

 in front, more obtuse posteriorly, and slightly inflexed on the ventral margin. 



V. Btthoctpeis, Brady, 1880. 

 In this genus the left is larger than the right valve. 



1. Bythocypeis SIMULATA {Joues). Plate I, figs. 27 — 29. 



Cytheee taba, Jones (not Reuss^). Monogr. Entom. Cret., 1849, p. 13, pi. ii, 



figs. 4 a — c. 

 — SIMULATA, Jones. Greol. Mag., 1870, p. 75. 



Length '77 ; height '88 ; thickness "33 mm. 



This is bean-shaped, tumid, and boldly arched, with an elliptical curve above; 

 sinuous on the ventral border, which is incurved at its anterior third, and highest 

 behind the middle of the valves. Anterior extremity rounded ; posterior, sub- 

 acute.^ 



' See the remarks by the late Dr. A. E. von Eeuss in the ' Zeitschr. d. D. g. G.,' vol vii, 

 1855, p. 278, on this species, and in the ' Elbthalgeb.,' &c., pt. ii, p. 142. The original figure of C.faha, 

 Eeuss, in the ' Bohm. Kreidef.,' although very poor, is certainly matched by this species better than 

 by any other that we know. Dr. Eeuss, however, found them to be difierent, and the name was 

 altered. 



2 Not drawn so perfectly in the reproduction, fig. 27, as in the former fig. 4 a. 



