Mr, F. M‘Coy on the Tail of Diplopterus. 139 
“On y trouve aussi des oiseaux de différentes espéeces, que lon 
7 prend souvent a 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 ; apprivoisé on le voit tou- 
jours marcher & la méme ligne, tant qwil a despace, et retro- 
grader de méme sans s’en écarter. Lorsqu’on en fait ouverture, 
on y trouve ordinairement des Bézoards, dont on fait cas, et qui 
sont utiles dans la médecine.” 
XV.—Reply to Sir Philip Egerton’s Letter on the Tail of Di- 
plopterus. By Freprrick M‘Coy, M.G.S. & N.H.S.D. &e. 
To the Editors of the Annals of Natural History. 
GENTLEMEN, Cambridge, Jan. 13th, 1849. 
Str Purire Eerrron 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 
im the November Number of your Journal, by remarking that 
Agassiz called the tail of Diplopterus ‘ heterocer eal,” 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 Egerton 
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 writings 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- 
quée presque verticalement, et /a colonne vertébrale finit a son 
angle supérieure ;” 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 figures 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 
