134 



Mr. R. H. Whitehouse. 



[Oct. 30, 



a,rea. While our " Motor A " corresponds in position fairly closely with his 

 Feldern 4 and 6 (area gigantopyramidalis and area frontalis agranularis), the 

 larger dots which in our figures represent the region in which the largest 

 pyramids may be found are spread over practically the same as his 

 Feldern 4. 



None of his types appears to correspond with our " Motor B." But 

 its position at its posterior end is occupied in his figure with the lower end 

 of his area post centralis (Feldern 1 to 3). Our post-central cortex occupies 

 much the same position as his area prseparietalis (Feldern 5), except that 

 it does not extend so far downwards on the lateral surface. With regard to 

 the temporal and olfactory regions we are in fair agreement.] 



The Caudal Fin of Fishes {Preliminary Paper). 

 By EicHARD H. Whitehouse, M.Sc. Birm. 



(Communicated by Prof. F. W. Gamble, D.Sc, F.R.S. Received October 30, — 



Read December 9, 1909.) 



CONTENTS. 



PAGE 



I. — Introduction 1.34 



II.— Types of Caudal Fin— 



1. Protocercy 135 



2. Heterocercy 136 



3. Hoinocercy 138 



4. Gephyrocercy 142 



III.— Morphology of Parts 142 



I. — Introduction. 



The aim of tlie present paper is to give, as concisely as possible, the 

 summary of two years' work on the caudal fins of fishes and also to revise the 

 ■definitions relating to the different types of caudal fin. The revision of the 

 definitions of old established names sucli as protocercy, heterocercy, etc., has 

 jtroved to be (piite essential owing to tlie vagiieness and even errors connected 

 with tliese terms so much in evidence in text-books of zoology; this vagueness 

 undoubtedly exists, or otherwise such mistakes us attnl)uting diphycercy to 

 such types as the Oadida; and tlic ccds would not oticur as they do. I have 

 also l)een assured l>y several eiiiinont teachers of zoology tliat the subject 

 needs clearing uj). 



