236 Mr. J. W. Hulke. On the Shoulder Girdle, 



shoulder girdle are, normally, never synostosed,* bat that the 

 scapulee and coracoids preserve their separate individuality even in 

 skeletons bearing the stamp of maturity, the inference is warrantable 

 that they were in life knit together by a persistent remnant of the 

 cartilaginous " continuum" which in Amphibia and upwards is the 

 foundation of these two bones, and also of the precoracoid where 

 this exists. 



Further, analogy warrants the inference that the quantity of such 

 persistent cartilage remaining at the ventral end of the scapula, and 

 at the corresponding tract of the coracoid, varied with the age of the 

 individual, and in dependence on this, with the extent to which ossi- 

 fication had advanced ; also that the quantity of this remaining 

 cartilage was not throughout its area a bond of uniform width, but 

 it was narrower where the bones it united approached, and wider 

 where they receded from one another. But the recess between the 

 truncated antero-external corner of the coracoid and the adjacent 

 antero-inferior angle of the scapula, both which parts bear, as Pro- 

 fessor H. Gr. Seeley says, the mark of having had cartilage attached 

 to them, is just the situation where a wider band of synchondrosial 

 cartilage might be expected than was present posteriorly where the 

 scapula and coracoid were nearer together. 



In support of his conception of a precoracoid cartilaginous in 

 Ichthyosauria, Professor H. Gr. Seeley cites the opinion held by Sir 

 E. Home, Bnckland, and Cuvier respecting the position and the rela- 

 tions of the scapula. These opinions are to be gathered chiefly from 

 their figures, since their text gives us little information of their 

 thoughts on the matter. 



Sir E. Home, in his third paper on Ichthyosaurian Remains,f says, 

 of the scapula in Mr. Bullock's specimen engraved in his first 

 paper, "it was then mistaken for a portion of a rib accidentally 

 brought there, but it is now found to have been nearly in its 

 natural situation. It bears a resemblance to the clavicular bone in 

 Birds." 



Sir E. Home's "reconstruction" of the Ichthyosaurian shoulder 

 girdle (fig. 1) was manifestly based on certain resemblances its com- 

 ponent parts showed to those of the " sternum " of Omithorhynchus 

 paradozus, which latter was brought to his attention by Mr. W. Clift, 

 Conservator of the Museum of the Royal College of Surgeons. Sir 

 E. Home unfortunately misread the Monotreme's pectoral girdle ; he 

 mistook its coracoid for a descending process of its scapula, and he 

 identified its epicoracoid with the Ichthyosaurian coracoid. 



* I have noticed synostosis of scapula and coracoid in IcUhyosawria as a sequel 

 of inflammation, marked by much irregular hyperostosis. 



t Home, Sir E., " Additional Facts respecting the Fossil Remains of an Animal," 

 ' 1818, p. 25. 





