﻿474 MESSRS. WHITE AND TREACHER ON THE [Aug. I905, 



Marsujoites-BsLTnl of the Margate district in Dr. Rowe's extensive 

 collection ; and in one stout, imperfect specimen the depth of the 

 cavity will even bear comparison with that exhibited by some 

 individuals of Actinocamax quadratus, from the Phosphatic Chalk 

 of Eeauval (Somme), Orville (Pas-de-Calais), and other French 

 localities, in the same collection. 



Dr. Rowe and Mr. G. C. Crick agree, however, in referring a 

 selection of the alveolated specimens (including the extreme types) 

 obtained by us from this part of the Taplow section to Actinocamax 

 granulatus (Blainville). 



The examples of Echinocorys scutatus, v&r.pyramidatus l — of which 

 we have eight in well-preserved condition, as many others capable 

 of identification, and the Museum of Practical Geology, Jermyn 

 Street, has, at least, two more — closely approach the shape-v a nations 

 commonly found in the higher part of the Marsujyites-B&nd in this 

 country; but all fall far short of the average in point of size. The 

 length and height of the largest complete test in our collection are 

 51*5 millimetres and 33 mm., and Of the smallest 30*5 mm. and 

 21 mm. respectively. The latter, as Dr. Rowe has pointed out to us, 

 closely resembles the dwarfed pyramidal form characteristic of the 

 lowest beds of the Actinocamax-quadratus Zone. Among the in- 

 complete examples there are still smaller forms. The second 

 variety is a depressed ovoid form, with a marked prolongation of 

 the posterior end. It is represented by a single complete example, 

 55*5 mm. in length and 31 mm. in height, and by another 

 fragmentary specimen, apparently of rather smaller dimensions. The 

 nearest affinity is probably the var. gibbus, for we find a rather 

 similar form merging into that variety in the Micraster cor- 

 testudindrium and Holaster-planus Zones of the Thames Valley. A 

 specimen somewhat resembling it is in the National Collection at 

 South Kensington, 2 and Dr. Rowe has seen similar forms (but 

 without the posterior development) in the base of the Actinocamax- 

 quadratus Zone, and also in beds of Micraster cor-anguinum age. 

 Rut, although it may be possible closely to match the individuals of 

 Echinocorys scutatus occurring in the higher beds of the Taplow 

 Phosphate from the normal Chalk, the whole facies of the species 

 there is an exceedingly-rare, if not a unique one, for this country. 



Remains of Echinocorys are plentiful throughout the Upper Brown 

 Chalk, and particularly so in the lower 3 feet, where, however, 

 we have obtained only stout fragments. 



Ostrea vesicidaris, by far the commonest macroscopic fossil at this 

 horizon, occurs singly, and in thin, closely-superposed seams. This, 

 or 0. Wegmanniana, is probably the form alluded to as ' 0. acuti- 

 rostris ' in previous accounts of the section. 



The largest example of Porosphcera globidaris is but 5 milli- 

 metres in diameter. 



1 See remarks on this variety in Dr. Eowe's ' Zones of the White Chalk of 

 the English Coast : Pt. IV— Yorkshire' Proc. Geol. Assoc, vol. xviii (1904) 

 pp. 255-56. 



2 No. 34693, from the ' Chalk '' of ' Kent.' 



