1907.] ox THE SCALES OF PISH. 751 



The following papers were read : — 



1. On the Scales of Fish, Living and Extinct, and their 

 importance in Classification. B}^ Edwin S. Goodrich^, 

 F.K.S., F.Z.S., Fellow o£ Merton College, Oxford. 



[Received November 12, 1907.] 

 (Plates XLIII.-XLVI.* and Text-figures 196-204.) 



In a recently pviblislied paper on the Dermal Fin-rays of Fish (3), 

 I remarked that the importance of the scales in classification 

 seemed not to have received the attention it deserved. A careful 

 study of the structure of the scales of living and extinct fish having 

 confirmed this opinion, an account is here given of the results of 

 my researches. Incomplete as these are, partly owing to the lack 

 of material, they will be sulficient, I think, to show that the 

 subject is full of interest, and well worthy of further study. 



For the material used in the investigations I am to a great 

 extent indebted to the genei-osity of various friends, among Avhom 

 may be mentioned Dr. Traquair, Prof. Sollas, and Mr. Boulenger ; 

 but especially do I wish to express my thanks to Dr. A. Smith 

 Woodward for help constantly rendered dui-ing my frequent visits 

 to the British Museum. 



Agassiz, in his classical memoirs on fossil fish (1), laid the 

 foundation of the modern work on fish-scales, and it is well-known 

 that he based his classification chiefly on their structure. But 

 less generally known is it that more than half a century ago 

 Williamson (26 & 27) published two most important papers on 

 the scales of _fish, of which he gave a very detailed and beautiful 

 account. Not only was he able in many ways to complete and 

 correct previous obsei-vations, to give the first accurate description 

 of the minute structure of the scales of living and extinct Selachii, 

 ' Ganoidii,' and Teleostei, but he also explained their mode of 

 growth, and brought forward a theory of the origin of the various 

 types of scales, aiad of their derivation from the primitive denticles 

 of the Elasmobranch. Indeed "Williamson's theory is in many 

 respects superior to those modifications of it which have since been 

 published by Hertwig (7), Klaatsch (10), and others. It may be 

 added that in these remarkable papers Williamson clearly dis- 

 tinguished calcification of cai'tilage in the Elasmobranch from the 

 various processes of the formation of true bone he desciibed in other 

 fish. His theories will be discussed later on (pp. 759-760) ; but 

 it may here be mentioned that he considered that the superficial 

 layer of the scale of Megalichthys is formed by the combination of 

 a layer of " cosmine," derived from denticles homologous with those 

 of Elasmobranchs, with deeper layers of bone of independent 

 origin. He believed the cosmine layer to be formed by the 

 concrescence of " dermal teeth." He further showed that the outer 



* For explanation of the Plates, see p. 774. 



