OF THE PURBECK POBMATION. 317 



but a form resembling our figs. 10 and 17, PI. IX., is figured by 

 Eomer (badly) and by Dunker from the Wealden of Obernkirchen 

 and the Purbeck limestone of the Deister, as C. granulosa, Sow. ; 

 and Eorbes's MS. sketch of granulosa (in Mr. Bristow's letter) also 

 approximates to fig. 17, PI. IX. 



Among Dr. Fitton's collection deposited in the Museum of the 

 Geological Society, there are mounted specimens of the G. tuherculata, 

 fig. 2 (pi. 21), and 0. spinigera, fig. 3, both Wealden species. There 

 are none mounted, however, of the forms represented by his figs. 1 

 & 4 ; but specimens like fig. 4 occur freely in some of the rock- 

 specimens preserved in that collection. 



For the specific names of the Cypridse mentioned and figured in 

 Dr. Fitton's memoir (1836) in only one case I refer to Fitton as the 

 authority. He especially states that he gives the name valclensis 

 at p. 177; but the other species were determined by J. de C. 

 Sowerby, and to him I refer as their authority, as, indeed, does 

 Dr. Dunker, though F. A. Eomer regarded them as Fitton's species. 



Interesting notes on the casts of " Cypris^' observed in the 

 Lower-Purbeck beds, overlying the Portland Stone at Portland, are 

 given at pp. 219 & 229 of Dr. Fitton's memoir " On the Strata 

 below the Chalk " &c., Trans. Geol. Soc. ser. 2, vol. iv. (1836) ; 

 but their importance is much lessened by the absence of definite 

 descriptions and figures. A species said to be near to C. spinigera, 

 and one with a " protuberance at the end of the valves," are indi- 

 cated. At p. 212 " C. tuberculata " and " 0. valclensis ? " are also 

 referred to as occurring at Portland, about 20 feet above the 

 Portland Stone*. The specific determinations of these little 

 organisms, however, were in many cases inaccurate in those days. 

 The Cypridiferous beds in the Purbeck of Bucks are noticed at 

 p. 297 ; of Wilts at pp. 259 & 260 ; of Dorset at p. 229. 



Other Collections. — The Purbeck specimens in the Museum of 

 Practical Geology and the British Museum have also been carefully 

 examined. The results are incorporated with the lists given in the 

 sequel. So, also, with specimens kindly communicated by the Eev. 

 0. Fisher, F.G.S., and W. Cunnington, Esq., F.G.S., as well as my 

 own large collection. 



§ III. The Osteacoda or Wealden and eeputed Wealden 

 Steata. 



Fitton, Sowerby, and Mantell. — In treating of the Purbeck 

 Ostracoda it is obviously necessary to have a preliminary notice of 

 the Wealden species so far as they have been described ; for some 

 of the forms recur in this upper formation, and most of the series 

 have some mutual relationships. Cypindea valdensis (Fitton), 

 Q. Austeni, Jones, C. tuberculata (Sow.), and C. spinigera (Sow.), 

 have been referred to above, being noticed in Fitton's memoir. 



In 1844 (' Medals of Creation,' vol. ii. p. 545, lign. 119, fig. 2) 



* Probably No. 389, further on, at p. 325, is such a specimen, definitely cha- 

 racterized by C. hononiensis, C. ansata, and C. purhecJcensis. 



