114 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



From this it would at first sight appear that these Barton beds 

 had more affinity with the Calcaire grossier than with the Sables 

 moyens, as the actual number of species common to the former is 

 greater than to the latter ; but it must be remembered that the 

 number of described Calcaire grossier shells is nearly double that of 

 the Sables moyens, consequently the relative proportion of common 

 species is greater with the latter beds, although the actual number 

 of Calcaire grossier forms is larger. Taking the number of Calcaire 

 grossier Testacea to be 65 1 and of the Sables moyens 377, the relative 

 per-centage proportion of the species of each of these groups occur- 

 ring at Barton is — 



Calcaire grossier 12'4 ; Sables moyens 21 ; or as 4 : 7 nearly. 



At the same time the question is rendered more involved by the 

 circumstance that there are as many as 18 Calcaire grossier species 

 which do not appear in the Bracklesham Sands, but which are found 

 in the Barton Clays * ; and in the same way there are several Brack- 

 lesham species which I do not find quoted from the Calcaire grossier, 

 but are found in tlie Sables moyens f . This shows how necessary 

 it is to take the entire group of organic remains, for, assuming the 

 species to be correctly determined, it seems impossible in nearly 

 related divisions of this description to found any sufficient argument 

 respecting the synchronism of the strata upon the occurrence of any 

 one or even several common species, although they may be ordinary 

 forms in one particular area. 



It is also to be observed that of the seven Corals described by M. 

 Milne-Edwards from Barton he has mentioned only one French 

 species, and that one from the Calcaire grossier, although the Sables 

 moyens are characterized by a considerable number of this class of 

 fossils. Further, one only of the six Barton Annelids, and none of 

 the eight Echinoderms have yet been recognized in the Sables moyens. 

 Of the few scarce Fishes, Reptiles, and larger Crustacea which occur 

 in both deposits, none have at the present time been determined to 

 be common to the two. All these, however, require a more careful 

 and extended comparison than has hitherto been made. 



The same with the Foraminifera : of the several species described 

 in the Sables moyens, only one, but that however a very character- 

 istic one, has yet been noted in the Barton Clay, viz. the Nummulites 

 variolarius. There are many other species, but the genera only have 

 yet been determined. 



The microscopic Crustacea have been determined by Mr. Rupert 

 Jones, to whom I am indebted for a list which shows that out of the 

 13 Barton species, there are 6 which are found in the Calcaire gros- 

 sier, and only 5 in the Sables moyens. 



* Including the following species : — Bulla coronata, Cerithium cinctum, Fas- 

 ciolaria funiculosa, Murex crispus, M. iripteroides, Strombus Bartonensis, Crassa- 

 tella sulcata, Lucina gigantea, Neara cochlearella, Vulsella deperdita, &c. 



f Including the Natica ponderosa, N. lineolata, Orbis patellatus, Valuta Bran- 

 deri, Mactra depressa, and Tellina lunulata. 



