Geological Society of London. 189 



Careful examination shows that this brecciated structure is due merely 

 to the rock having been crushed and the fragments connected in situ 

 by siliceous infiltrations. Delesse's observations upon the varieties 

 of the rock were discussed. A few additional remarks were also 

 made upon the mineral constitution of the specimens described. 



4. " Fossil Chilostomatous Bryozoa from Aldinga and the River- 

 Murray Cliffs, South Australia." By Arthur William Waters, Esq., 

 F.G.S. 



The 73 fossils described in the present paper were collected by 

 Professor Ralph Tate, and, with a few exceptions, are from Aldinga 

 and the River-Murray Cliffs, Austi'alia. 



This collection again furnishes interesting cases of species growing 

 in both the Eschara and the Lepralia form ; but the chief interest 

 is in a number of specimens which grow in a "cupulata" manner, 

 thus in the mode of growth resembling Lunulites. Attention was 

 again called to the fact that though the shape and nature of the 

 zooecial avicularia (onychocellaria) are characters of the greatest 

 value, yet their presence or absence cannot be made a specific dis- 

 tinction, as there are a large number of cases where specimens are 

 found with none or only a few such avicularia, whereas on other 

 specimens of the same species, collected under similar circumstances, 

 they may occur abundantly over the whole colony, or in parts of the 

 colony, in large numbers. 



In the " Challenger " Report, Mr. Busk refers to a slender process 

 rising from the middle of the base of the avicularian mandible, and 

 names it " columella." This he considers only occurs in one division 

 of the Celleporoe, and in this division only in those belonging to the 

 southern hemisphere. This was shown to be by no means the case, 

 as it is found in the mandibles of Celleporce sardonica from the 

 Mediterranean, in two other common Mediterranean Cellepo7-ce, etc. 

 In many species there is a denticle in this position rising from the 

 calcareous bar which divides the avicularium. This denticle occurs 

 in various genera and species, and may often be found a useful 

 specific character when examining fossils. 



Out of the 220 species now described in this series of papers, just 

 about one-half are now known living. 



The species noticed in this paper are 73 in number, referred by 

 the author to the genera Cellaria, Membranipora, Micropora, Mono- 

 porella, Steganoporella, Crihrilina, Mucronella, Microporella, Lunulites, 

 Porina, Lepralia, Smittia, Schizoporella, Mastigophora, Betepora, 

 Bhi/nchopora, Cellepora, Lelcijtliopora and Selenaria. Five species 

 are described as new, namely, Microporella pocilliformis, Lepralia 

 confinita, Cellepora biradiata, Schizoporella protensa, and Membrani- 

 pora temporaria. 



