54 Sir Philip Egerton on the Tail o/Diplopterus. 



gret to be again obliged to notice an omission no less unjust to 

 Professor Agassiz. In the November Number of the * Annals/ 

 Mr. M'Coy, when treating of the tail of Diplopterus, says : — 

 " M. Agassiz has described the species of this genus as having 

 heterocercal tails/^ leaving it naturally to be inferred, that these 

 fishes had the ordinary form of tail common to many of the older 

 ganoids. He then proceeds to state, that so far from this being 

 the case, "there is almost as great a development of fin- rays 

 above as below the spinal prolongation." This form of tail, in- 

 termediate in appearance between the homocercal and hetero- 

 cercal types, he proposes to style "diphy cereal.'^ The following 

 passage from the ' Fossil Fishes of the Old Red Sandstone,^ p. 54, 

 shows how fairly ! Agassiz's description has been stated by Mr. 

 i\I'Coy in reference to this modification of the caudal fin : — " La 

 caudale a une conformation des plus singulieres. II va sans dire 

 qu'elle est heterocerque, et que la masse principale des rayons 

 est inseree sous le prolongement releve de la colonne vertebrale ; 

 mais au bord superieure il y a au lieu de fulcres de veritables 

 rayons, en grande quantite, si bien que le prolongement de la 

 colonne vertebrale se trouve garni de rayons en haut comme en 

 has." Fig. 1. of tab. 18 gives a very good I'epresentation of the 

 peculiarity described in the text. Now although the more per- 

 fect specimens examined by Mr. M'Coy may have enabled him 

 to trace this modification to a greater extent, yet, in all fairness, 

 he ought to have alluded to the facts established by Agassiz in 

 the passage quoted above. I prefer again to attribute this seem- 

 ing unfairness to forgetfulness of Agassiz's writings, rather than 

 to intentional disregard of them, an opinion which is strengthened 

 by the occurrence in Mr. M'Coy^s writings of the cancelled spe- 

 cific appellation latus, when speaking of Coccosteus decipiens. 

 The remarks on the gradations of structure between the two 

 types of tail, appended in a note to Mr. M'Coy's paper, and 

 stated to have been also noticed by Miiller, were made by the 

 Professor so long ago as 1844, so that his claim to priority and 

 not only to simultaneity of discovery is unquestionable. In con- 

 clusion, I must beg to disclaim any the slightest intention of 

 giving annoyance to Mr. M'Coy, or of underrating in any degree 

 the value of his ichthyologic investigations. I am only anxious 

 that justice should be done to those who through absence are 

 unable to vindicate their own rights until it may be too late to 

 do so with effect. 

 I have the honour to be. Gentlemen, your obedient servant, 



Philip de Malpas Grey Egerton. 



