OF THE PT7RBECK FOBMATION. 315 



There is no special order kept in this list. The false margin is 

 partly indicated for jpurheclcensis, and the name granulata, as in 

 Ly ell's list (fig. 371, c), is probably given by mistake for granulosa 

 of Eomer and Dunker. 



The Vertical Sections jpuhlislied hy the Geological Survey. — Only 

 three " Cyprides " with specific names (tuberculata, leguminella, and 

 pm-becJcensis) are affixed to any particular bed in the Geological 

 Survey's "Vertical Sections " (Sheet No. 22) of the Purbeck strata, 

 made after Prof. E. Porbes had finished his survey-work. In the 

 successional table of the strata seen at Dnrlston Bay there are six 

 Cypridiferous beds, or groups of beds, indicated for the " Upper 

 Purbeck," the topmost containing "O. tuberculata ;" for the " Middle 

 Purbeck" twelve such beds; and for the "Lower Purbeck" two 

 such special zones. Among the strata seen at Worbarrow Bay 

 there are indicated one such bed for the " Upper," two for the 

 " Middle," and five for the " Lower Purbeck ; " at Mewps Bay, 

 one for the " Upper," three for the " Middle," and three for the 

 " Lower Purbeck." For the section at Ridgway Hill, north of 

 Weymouth, there are two such zones in the " Upper ;" four in the 

 " Middle," in one of which '' C. leguminella " is named ; and six in 

 the "Lower Purbeck," in the uppermost of which " O. purbecJcensis " 

 is mentioned. 



The persistency of several of these Cypridiferous zones throughout 

 the Dorsetshire sections is very noteworthy. How far the same 

 species of Ostracoda hold their own along these zoces is not yet 

 determined ; but possibly the appended lists (though imperfect) will 

 throw some light on this subject. 



Lists of Purbeck Strata by H. W. Bristoiu, J. H. Austen, and 

 0. Fisher. — In Mr. Bristow's Purbeck list, in the new edition of 

 Damon's ' Geology of Weymouth ' &c., 1884, pp. 202, 207, & 209, 

 the species referred to the three divisions of the Purbeck series are 

 the same as in LyeU's ' Manual ' above quoted. No '* Cyprides " 

 are specially mentioned in the Rev. J. H. Austen's list* in his 

 ' Guide to the Geology of the Isle of Purbeck ' &c., 1852 ; or in 

 the Rev. 0. Pisher's list of the strata at Swanage Bay, Trans. Camb. 

 Phil. Soc. vol. ix. p. 568 &c., 1855 ; but in his list of the strata at 

 Ridgway Hill, " Cypris purbecJcensis " is affixed to one of the Lower 

 Purbeck beds. Both the Rev. 0. Pisher and Mr. Cunnington have 

 favoured me with named specimens of G. purbecJcensis and G. 

 fasciculata. 



Fitton and Sowerby; and Dr. Fitton's Specimens in the Museum 

 of the Geological Society. — Of the Cypridae referred by Pitton in 

 1836 to the Purbeck formation, unfortunately we cannot speak 

 with full certainty. 



Gypridea valdensis (Fitton), first and erroneously referred by 

 J. de C. Sowerby to Gypris faba, Desmarest, was figured and 

 described by him (1824) in the ' Mineral Conchology,' pp. 136-138, 



* In G. Wilson and A. Geikie's ' Life of Edward Forbes' (1861) it is sug- 

 gested, at p. 477, note, that this list was based on information obtained from 

 the Geological Surveyors. 



