310 



A. W. WATERS ON FOSSIL CHILOSTOMATOITS 



any result. The few molluscan shells are probably fry, and do not 

 give much assistance, but support the " Miocene " age of the beds. 

 There are also a few Entomostraca. 



The fragments of Bryozoa are small ; but their state of preserva- 

 tion is often very perfect ; and in this lies their chief value. Their 

 examination may well be used as an introduction to the study 

 of the Mount-Ganibier series of Australia, in which, so far as I am 

 able to judge from the London Geological Society's collection, kindly 

 lent to me, and from a collection belonging to Mr. Etheridge, 

 jun., also in my hands, the state of preservation often does not 

 admit of the details being seen ; so that the determination and de- 

 scription of these is sometimes very unsatisfactory if other material 

 is not at hand to be used as a key to the structure. As examples I 

 may mention Microporella yarraensis, M. violacea, var., Porina cly- 

 peata, and Hetepora rimata, which occur in the Mount-Gambier beds ; 

 but the details are wanting, and were it not for the " Yarra-Yarra " 

 specimens I should have been unable to classify them. 



The living British Bryozoa have recently been reclassified by 

 Mr. Hincks, who has introduced in some sections an almost new 

 classification. Since the appearance of his work no palaeontogical 

 papers of any importance have appeared ; and it therefore becomes 

 necessary to consider how far this classification is applicable in the 

 determination of fossils ; and it is here that we shall perhaps find the 

 weak point in the modern classification : but, on the other hand, 

 fossils more than recent forms show the utter unnaturalness of the 

 older divisions. Although generic determination will often be diffi- 

 cult, that is by no means confined to the present system ; for we often 

 find fragments showing many important characters without being- 

 able to distinguish if they have grown in the Eschar a or Lepralia 

 form. Every change of classification should, of course, aim at 

 making the system more natural ; but at the same time special 

 attention should be given to those characters which can be distin- 

 guished in fossils, seeing that the number of known fossil forms is 

 so many times more than all the known recent ones, and ultimately 

 the relationship of the living ones must be worked out largely by 

 means of the palseontological record. 



In the classification used by Busk in his 'Crag Polyzoa/ and, with 

 some modifications, by Reuss, the form of the colonial growth was 

 made the first consideration ; so that colonies of cells of a certain 

 form incrusting stones or seaweed were called Lepralia, while quite 

 similar cells, growing back to back, forming an erect coral-like 

 stem, would be called Eschar a or, if there was only one layer, 

 Hemescliara. With more careful examination and comparison of 

 recent and fossil forms this was found to be an absolutely untenable 

 position, as the same forms of cells so frequently occur that any one 

 well acquainted with recent and fossil Bryozoa could in a short time 

 draw up a list of at least 40 or 50 cases where absolutely identical 

 cells are known in the Lepralia and Eschara forms. Smitt *, recog- 



* Krit. Fort, ofver Skandiuaviens Hafs-Bryozoerne, af F. A. Smitt. Ofv. 

 Vet. Ak. Forhandl. 1864-1868. 



