14 The Marsupites Chalk of Brighton. 



the last stone groin at Black Bock. The greater part of it then 

 passes out of sight fairly quickly under the combined influence of an 

 easterly dip and the rise of a shingle bank ; but once the thick flint 

 seam which forms its upper boundary has reached the shingle level it 

 continues at about that level, appearing and disappearing, for quite 

 a quarter of a mile before a further rise of the shingle hides it finally, 

 so that there is a long exposure of the Uintacrinus band. 



Bed 2 appears to be quite devoid of crinoid remains, and in 

 accordance with my practice elsewhere I assign it to the Uinta- 

 crinus band. 



Bed 3 embraces all the chalk yielding undoubted plates of 

 Marsupites. It appears to be uniformly poor in fossils as compared 

 at any rate with the Marsupites chalk of Hants and Kent, and 

 especially so in the lower beds. The same progression in the plates 

 of Marsupites from dwarf and smooth plates up to large and 

 elaborately ornamented plates which appears to exist in Hants can 

 be traced here, though not so well as in Kent, as noted by Dr. Bo we. 1 

 The retrogression in size, accompanied by intensification for a time in 

 ornament ending in a sudden brief return to smoothness, which 

 appears to take place in the upper beds in Hants, can be more or less 

 recognized here also. 



Bed 4 is the one which I specially discussed in the August number 

 of this Magazine (pp. 361, 362), and which yields brachials and curious 

 plates of crinoids. Brachials are distinctly more numerous here than 

 is usual in Marsupites-chaYk, but less numerous than is usual in 

 Uintaerinus-chaYk. They seem to me indistinguishable from those 

 which accompany plates of Marsupites (and Uintacrinus), but after 

 close examination of all the plates from this bed I am not able to 

 assign one of them satisfactorily to Marsupites. They appear to be 

 all more or less related, and I am left with a strong impression that 

 they represent a third crinoid distinct from but generally resembling 

 Marsupites and (in a stronger degree) our common species of Uintacrinus, 

 and being possibly another species of the latter genus. If so it would 

 not alter my view that the affinities of the bed are far more strongly 

 with the zone of Marsupites than the subzone of E. seutatus, var. 

 depressus, and that it should be included with the former. With it 

 must go Bed 5, from which I have now a number of brachials and one of 

 the peculiar plates. (In the August number of this Magazine I left 

 this latter bed in the subzone of JE. seutatus, var. depressus, thereby 

 securing a physically definite boundary at what was then a very small 

 sacrifice of palseontological principle.) 



It is interesting to note that the Marsupites-chaYk of Kent is 

 crowned by a bed which appears to be more fossiliferous than this 

 Sussex bed, but corresponds very closely in its fauna. The only 

 noticeable point of difference is that Hagenowia rostrata, which has 

 not yet occurred at this horizon in Sussex, is abundant there in Kent. 

 This is, however, only what might be expected from the relative 

 frequency of this fossil at lower levels in Kent as compared with 

 Sussex, where I know of no specimen below the zone of 0. pilula 

 and only one in it. 



1 " Coast Sections," pt. i, p. 297. 



