Mr. F. M'Coy on the Tail o/Diplopterus. 139 



" On y troLive aussi des oiseaux de differentes especcs, que Ton 

 preud souvent h la course, et entre autres des Solitaires, qui 

 n'ont presqu' point de plumes aux ailes; cet oiseau, plus gros 

 qu'un Cygne, a la physionomie triste ; apprivoise on le voit tou- 

 jours marcher k la meme ligne, tant qu'il a d'espace, et retro- 

 grader de meme sans s^en ecarter. Lorsqu'on en fait Fouverture, 

 on y trouve ordinairement des Bezoards, dont on fait cas, et qui 

 sont utiles dans la medecine." 



XV. — Rephj to Sir Philip Egerton's Letter on the Tail of Di- 

 plopterus. By Frederick M'Coy, M.G.S. & N.H.S.D. &c. 



To the Editors of the Annals of Natural History. 



Gentlemen, Cambiidge, Jan. 13th, 1849. 



Sir Philip Egerton has written a letter in your last Number, 

 from which it would appear that I had acted unfairly towards 

 Prof. Agassiz in my description of the diphycercal type of tail 

 in the November Number of youi" Journal, by remarking that 

 Agassiz called the tail of Diplopterus ' heterocercal,'' and leaving 

 it to be inferred that the ordinary heterocercal form was intended. 

 Sir P. Egerton does not deny the accuracy of my description and 

 figure of the tail of this genus and its difference from the true 

 heterocercal type ; and though no one comparing them with 

 Agassiz^s work will see any resemblance, yet Sir Philip Egercou 

 endeavours to show that Agassiz gave the same characters that 

 I do, by suppressing in his letter all allusions to those passages 

 in Agassiz's wi'itings which state without reserve that the genus 

 was heterocercal, and by quoting a certain passage (giving a 

 very imperfect notion of the tail however) in which the exist- 

 ence of rays above the spine is mentioned. I will not ask why 

 Sir Philip Egerton only gave you the quotation from Agassiz's 

 work as far as he did ? or why he did not quote it entire ? But 

 I supply the missing line of the quotation : "^ La caudale est tron- 

 quee presque verticalement, et la colonne vertebrate finit a son 

 angle superieure -j" and I may add to this (what Sir P. Egerton 

 also omits to mention), that in the restored figure of the genus 

 (tab. E), combining his latest information in the same work, 

 Agassiz figm-es Diplopterus with a heterocercal tail perfectly iden- 

 tical with that of Osteolepis figured on the same plate, which is 

 one of the most perfectly heterocercal fishes we know. This 

 figure too is in accordance with the above omitted portion of the 

 quotation, and with the prevailing theory that none but hetero- 

 cercal-tailed fishes lived at those ancient periods ; it shows that 

 the quotation given by Sir P. Egerton did not imply a knowledge 



