150 Prof. H. G. Seeley. The Shoulder Girdle and [June 



. 



F.R.S., received by the Royal Society April 11, read May 12, 1892. 

 All that was then before the Fellows is printed in the Proceed- 

 ings for August 26, 1892, p. 471, and the paper was printed in 

 !S~o. 316 of the Proceedings. As my own paper had not been pub- 

 lished when that by Mr. Hulke was read, and as his paper is entirely 

 devoted to controverting my conclusions and discrediting the 

 existence of evidence which is there figured, it is obviously based 

 upon an imperfect knowledge of the facts. I should have been 

 content to have left the vindication of the truths and ideas which I 

 endeavoured to state to others, but that I had no opportunity of 

 meeting the author's contentions, when the abstract of his paper was 

 read ; and because there are misconceptions of my meaning, some of 

 which I should be glad to remove. The point of view taken by Mr. 

 Hulke as the foundation for his criticisms is said to be mainly 

 embryological work upon existing Reptiles and Amphibians, the 

 exact relation of which to the extinct Ichthyosauria and Sauroptery- 

 gia cannot be stated with precision, though all writers concede that 

 the groups compared, Urodela, Ariura, Lacertilia, are distinct orders ; 

 and I believe that the differences between them are too great to be 

 expressed in this way. The embryology of Ichthyosaurs and Plesio- 

 saurs being necessarily unknown, it seems to me that no sound inter- 

 pretation of the obscure parts of their skeletons can be based upon such 

 evidence ; unless it is previously shown that there is a predominant 

 affinity of the extinct organic type with the recent type to which it is 

 compared. I should, therefore, attach less value than does Mr. Hulke 

 to the embryological considerations which he adduces in relation to 

 the identification of bones as being omosternal on the one hand, or 

 clavicular on the other, and as determining the existence or absence 

 of a precoracoid element in these extinct animals. Rather than 

 import into discussion such hypothetical foundations for nomenclature 

 of the bones of the skeleton in extinct animals, I prefer to trust to 

 visible evidence of the relative position of the disputed bones, and to 

 such comparisons with their condition in allied animals a& may 

 appear to justify inferences as to their true nature. 



In discussing the shoulder girdle in Ichthyosauria, I have suggested 

 that the conditions of the bones appear to indicate a precoracoid 

 element, which was cartilaginous, and was not preserved. I assume 

 that such an element may have extended from the scapula to the 

 coracoid, transversely in front of the coracoid, and anteriorly between 

 it and the clavicle. To this suggestion Mr. Hulke replies that the 

 appearance of a division of the articular end of the scapula into 

 three parts is fallacious (loc. cit., p. 234) and illusory (p. 235). The 

 basis for this statement is said to be a careful study of many Ichthyo- 

 saurian scapulae, and especially of a separate scapula lent by Mr. A. N". 

 Leeds, F.G.S. Mr. Hulke finds that the Oxford Clay scapula com- 



