282 J. P. BLAKE AND W. H. HUDLESTON ON 



Astarte polymorpha, Lucina aliena, Modiola varians, Mytilus pecti- 

 natus, Perna mytiloides, Pholadomya cequcilis, Pecten quahcosta, 

 Ostrea gregaria (abundant), Exogyra nana, Chemnitzia hedding- 

 tonensis, and Nerita minuta. The mixed character of this fauna 

 shows that where the conditions remained constant no satisfactory 

 divisions can be made out, but that the whole must be taken as 

 equivalent to the period which elsewhere developed the false- 

 bedded series to the upper limestone inclusive. 



With rogard to the north beyond Gillingham, the Sturminster 

 section seems to be little guide above the pisolites ; for though there 

 is here a considerable amount of limestone, which from its nearly 

 horizontal lie covers much of the country, it cannot be identified 

 either with the false-bedded or the rubbly series. We have here 

 probably a distinct area of deposition, in which again calcareous 

 conditions largely prevailed, though not developing beds of the same 

 character in points of detail as those at Sturminster. The openings 

 made for the extraction of roadstone in this district are very shallow, 

 and they exhibit rocks of the same character for some distance across 

 the strike. 



The lower portion, which is probably not much above the pisolites 

 of Cucklington, may be illustrated by a quarry at Laugham. 



Section at Langliam. 



ft. in. 



1. Rubbly grit, with Ammonites cordatus, Belemnites abbreviatus, 



Perna quadrat a 1 



2. White oolitic marl with abundance of Natica clio 2 



3. Hard gritty limestone, used for roadstone, broken and irregular at 



the top, with Ammonites, sp. (Schilli), Phasianella striata, Chem- 

 nitzia heddingtonensis, Trigonia, clavellate sp., Gervillia avicu- 

 loides, Perna quadrata, Modiola 3 



The Cephalopoda here are quite strange to the district, but else- 

 where belong generally to low horizons. The characteristic fossils 

 are the Natica, Gervillia, and Perna ; these are in great abundance, 

 and together point to a time certainly previous to the Trigonia-heds 

 of Weymouth or the rubbly limestone of Sturminster. 



The upper portion of the Corallian beds in this part of the country 

 may be studied in similar openings further to the east, on the west 

 side of the river Stour, near Preston. We here see some 12 feet of 

 sandy oolites weathering in flaggy beds, but with a tendency to run, 

 as it were, into large doggers. The character of the stone is not 

 unlike that of the fine-grained Osmington oolites. It is remarkable 

 as containing a vast number of short fragments of narrow algse, 

 evidently floated from a distance. The brown marks made by these 

 on the white stone render it very conspicuous. With this excep- 

 tion the stone is not very fossiliferous, but contains a clavellate 

 Trigonia, Perna quadrata, Gervillia avicidoides, CJiemnitzia, sp., 

 Echinobrissus scutatus, and Exogyra nana. These fossils link the 

 rocks containing them to the series just described to the west. 

 These rocks, however, are overlain by still more noteworthy ones, 

 consisting of what may almost be called shell-beds, so numerous are 

 the fossils. Where these are small the matrix is still a sandy oolite ; 



