0)1 the Bones of the Sternum of young Tortoises. 319 



XLII. — Additional Notes on the Form of the Bones in the 

 8ter7iuvi of very young Tortoises^ and their Development. 

 By Dr, J. E. Gray, F.R.S. &c. 

 [Plate XII.] 



The British Museum having received some young tortoises 

 from North America, presented by the Smithsonian Institution, 

 I have been induced to examine the form of the bones of the 

 their sterna — and also the bones of the sterna of other young 

 specimens that are in the Museum, some of which have been 

 received since my former paper. 



As many of these specimens were in spirit before they were 

 examined, it is necessary to observe that if the sternum is looked 

 at as it is taken out of spirit, even when perfectly cleaned 

 inside, it appears to be a uniform opaque disk, and the form 

 of the bones cannot be observed even when held up to the 

 light — until it is dried, when the cartilaginous part becomes 

 transparent, showing the opaque bones ; and it becomes again 

 opaque when again placed in proof spirit. 



I have had great difficulty in obtaining young specimens 

 for the purpose of determining the development of the bones of 

 the sternum, and have thought myself very fortunate when I 

 have obtained one or two of a species ; and I thought that 

 this arose from collectors thinking that young specimens 

 would not be so much esteemed by Museum-directors as 

 the others. But Prof. Agassiz, who lives and has collected 

 in the country where tortoises are abundant, observes that the 

 young Emydes live almost exclusively in water, much more 

 so than their parents ; and though the young are naturally in 

 much larger numbers than the adults, they are still so rarely 

 found that they are almost unknown to zoologists. He 

 observes : — " For example, Emys insculpta is so common in 

 the neighbourhood of Lancaster that I have collected more 

 than a hundred specimens in one afternoon, and yet I have 

 never been able to obtain one of the first year, though a 

 whole school of young men were called in to search. Prof. 

 Baird has found the same difficulty in obtaining young Emys 

 rugosa for me, and though he offered a high price for them he 

 could not obtain more than a single specimen of the first year ; 

 and yet this species is so common that, in the season, hundreds 

 are daily brought to the market of Washington." ('Contribu- 

 tions,' i. p. 294.) 



I have also been able to examine the sternum of the very 

 young of two genera of land-tortoises that I had not before 

 been able to examine and therefore to add them to my previous 

 paper. 



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