344 Mr. F. Chapman on Ostracoda 



Cytherella Muensteri (Romer). 



Cytherina Muensteri, Romer, 1838, Neues Jahrb. fiir. Min. &c. p. 516, 



pi. vi. fig. 13. 

 Cytherella Muensteri, Jones and Hinde, 1890, Suppl. Mon. Cret. Entom. 



pp. 46, 47, pi. iii. figs. 63-67. 



The geological range of this common Cretaceous form is 

 from the Gault to the Upper Chalk, and somewhat similar 

 specimens have also been found in the Eocene beds of 

 Bracklesham Bay, Sussex. 



C. Muensteri is already known from the Cambridge Green- 

 sand, and it is common at Swaffham. 



It is probable that the specimen recorded from the Gault 

 of Folkestone as Cytheropteron folkestoniense* is a deformed 

 or unusual variety of the above species of Cytherella. There 

 is a somewhat similar variation shown in Dr. G. S. Brady's 

 Report on the ' Challenger ' Ostracoda \ in the species Cythe- 

 rella punctata, Brady, and referred to as the young form by 

 that author. 



Cytherella Williamsoniana, Jones. 



■Cytherella Williamsoniana, Jones, 1849, Mon. Entom. Cret. p. 31, 

 pi. vii. figs. 2Qa-h (and fig. 26 i, var. I; Jones and Hinde, 1890, 

 Suppl. Mon. Cret. Entom. p. 48, pi. iii. figs. 55-62. 



This species begins to make its appearance in the Gault 

 formation as far down as zone v. at Folkestone. The type 

 form is found through all succeeding strata to the Upper 

 Chalk. It has not been found before in the Cambridge 

 Greensand. At Swaffham it is of frequent occurrence. 



Cytherella Williamsoniana, Jones, var. stricta, 

 Jones and Hinde. 



Cytherella Williamsoniana, Jones, var. stricta, Jones and Hinde, 1890, 

 Suppl. Mon. Cret. Entom. pp. 48, 49, pi. iii. fig. 71. 



The carapace of this variety generally exhibits a greater 

 proportionate length than the type form, as well as having 

 distinctive sharp ridges. It is fairly common in the Green- 

 sand at Swaffham. 



C. Williamsoniana, var. stricta, was originally described 

 from Gault specimens. In that formation it begins to make 

 its appearance in zone v. at Folkestone. 



* Geol. Mag. 1893, vol. x. p. 349, pi. xiv. fig. 13. 



t ' Challenger' Reports, 1880, Zoology, part iii. p. 174, pi. xliv. fig. 4e. 



