THE 



SHOULDER-GIRDLE AND BREAST-BONE, 



INTEODUCTOEY EEMAEKS. 



THE germ of the present Memoir will be found in the ' Proceedings of the Zoological 

 Society/ June 28th, 1864 (Part 3, pp. 339 341), and, for the most part, the observations re- 

 corded here are merely a development of those to be found in that brief report. 



I was not aware, at the time when I read that paper, that the real nature of the Tortoise's 

 " plastron " had been discovered by the late Professor Rathke many years before ; but as early as 

 1848 he had given a true account of its structure (see his Memoir 'Ueber die Entwickelung 

 der Schildkroten/ pp. 122 131); when I come to the Chelonia I shall insert a translation of 

 his remarks on that subject. 



In my small paper there is a very grave error, which I discovered too late to correct. I 

 supposed that the "furcula" of the Bird answered to the azygous "episternum" (so-called) of 

 the Lizard, 1 whereas that bone includes both the " episternum " and the clavicles. 



This error led to another. I supposed the clavicles of the Lizard to answer to the antero- 

 inferior shoulder-bars of the Frog, which belong to the " coracoid " category, although they have 

 often been confounded with the clavicles. 



Nor had I discovered, when my abstract was printed, that the foremost bones of the 

 Tortoise's " plastron " are the true homologues of the three shoulder-splints of the Lizard, the 

 Bird, and the Monotreme ; nor that the two outer ones the so-called " episternal " pieces are 



1 Dr. Gray makes a similar mistake with regard to the " episternum " of the Monotremes (see 

 ' Zool. Proc.,' part ii, 1865, p. 385) ; he calls it the " furcula." 

 1 



