﻿468 MESSRS. WHITE AND TREACHER ON THE [Aug. 1905, 



are to be observed the strongly-undulate upper surface, with its 

 coarse brown enamel or glazing, encrusting Serpulaz and Plicatulce, 

 and agglutinated foraminiferal, coprolitic, and other remains ; the 

 innumerable minute and larger perforations (many of the former 

 being empty) ; the iron-staining ; the minute rhombs of clear 

 calcite ; the clustering dendrites of manganese-dioxide, — in short 

 all, or nearly all those features which characterize the hardened 

 layer usually forming the floor of the thicker masses of Phosphatic 

 Chalk in the North of Prance. 1 



The substance forming the glaze above described appears to be 

 nearly-pure calcium-phosphate. It varies from the merest film to 

 a mammillated crust from a sixteenth to an eighth of an inch thick, 

 enveloping and penetrating the small fossils which adhere to the 

 upper surface of the rock-bed, and descending into fissures in the 

 ]atter. The relations of this mineral to the above-described borings 

 are remarkably variable and interesting. Commonly sealing-up 

 the mouths of these tubes, it not infrequently forms a sort of 

 selvage to their soft contents for a depth of from 1 to 6 inches 

 below their upper ends ; but in many cases it has permeated and 

 hardened the brown chalk within them, while in other instances it 

 has left both the walls and the contents of the borings unaltered. 

 It is clear that the glazing post-dates the filling of some of the 

 borings, at least, and, to judge from appearances, also the indura- 

 tion of the rock-bed. 



The following is a list of the fossils obtained by us from this 

 division (A). 



[Note.— In this and succeeding lists the letters r. c. = rather common; 

 c. = common ; v. c. = very common. Species not so qualified may be regarded 

 as rare.] 



Pisces, (c.) 



Corax falcatus, Ag. 



Inoceramus Cuvieri, Sow. (v. c.) 



Lima (Plagiostoma) cretacea (?) Woods. 



Ostrea spp. 



Pecten (Neithea) quinquecostatus, 



Sow. 

 Teredo amphisbcsna, Sow. 

 Crania parisiensis, Defr. 

 Cidaris clavigera, Koenig. 

 Cidaris sceptrifera, Mant. 

 Terebratulina striata, Wahl. 

 Membranipora sp. 

 Echinocorys scutatus, Leske. 

 Galerites albogalerus, Leske. 



The majority of these were collected in the upper half of the 

 division (that is, within 8 feet of the top), from the white chalk 

 between the borings. The lower half yielded little but remains of 

 Inoceramus. 



Bourgueticrinus is represented by very small columnal and 

 brachial ossicles, and Echinocorys scutatus by fragments of medium 

 thickness. 



1 See J. Gosselet, Ann. Soc. Geol. du Nord, vol. xxiv (1896) pis. ii & iii. 



Asteroidea. (r. c.) 



Micraster cor-anguinum, Klein, (r. c.) 



Micraster cor-anguinum, var. latior, 



Eowe. 

 Bourgueticrinus ellipticas, Miller. 

 Porosphcera globularis, Phil. 

 Porosphcera patelliformis, Hinde. 

 Coscinopora infundibuliformis, Goldf. 

 Plocoscyphia convoluta, T. Smith. 

 Ventriculites alcyonoides, Mant. 

 Ventriculites decurrens, T. Smith, (c.) 

 Ventriculites infundibuliformis (?) 



S. P. Woodw. (r. c.) 

 Ventriculites radiatus, Mant. 



