THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[FOURTH SERIES.] 

 No. 95. NOVEMBER 1875. 



XXXIX. — Contributions to the Study of the chief Generic 

 Types of the Palaeozoic Corals. By James THOMSON, 

 F.G.S., and H. Alleyne Nicholson, M.D., D.Sc, 

 F.R.S.E., Professor of Natural History in the University 

 of St. Andrews. 



Introduction. 



The object of the present communication is to consider briefly 

 the characters of the leading types of structure which may be 

 recognized amongst the Palaeozoic Corals, irrespective of the 

 question as to whether these types constitute what would 

 technically be called u genera " or not. Indeed, as we shall 

 hereafter point out at greater length, the modern development 

 of the doctrine of Evolution has rendered any rigid definition 

 of what constitutes a "genus" an entire impossibility. So 

 far as this point is concerned, each observer must be left, 

 within certain limits, very much to his own judgment. In 

 carrying out the purpose which we have at present in view, 

 it is most convenient to adopt a stratigraphical rather than a 

 zoological arrangement ; and we shall therefore commence with 

 those genera which occur in the Carboniferous period. It may 

 be added that only those types will be considered of which the 

 material now in our hands is sufficient to allow of something- 

 like a complete elucidation. 



The method of investigation pursued has, in the main, con- 

 sisted in slicing and polishing the specimens in different 

 directions, and in preparing thin sections for microscopic ex- 



Ann. & Mag. N. Hist. Ser. 4. Vol. xvi. 22 



