92 H. H. NEWMAN. 



Some rather remarkable conclusions are expressed in Gadow's 

 paper and should be discussed in this place. 



1. He makes the following statement : "Abnormalities are 4 to 

 7 times as common in new-born as in mature specimens, hence 

 scute reduction must take place during the lifetime of the indi- 

 vidual." I have not had the opportunity of putting this matter 

 to a test in the case of TJialassoclielys, but the examination of 

 several complete nests of Graptemys has brought to light the 

 following facts. Two nests containing respectively thirteen and 

 fourteen embryos showed no abnormalities. One nest contain- 

 ing fourteen just-hatched young showed one slight abnormality, 

 a vestigial no. 10 costal. A fourth nest in which twelve eggs 

 came to maturity contained five decidedly abnormal specimens, 

 listed as nos. 11, 19, 25, 26 and 48. This means that barely 

 10 per cent, of the embryos of four broods are abnormal, while 

 out of 476 specimens of Graptemys 48 were abnormal in the 

 carapace scutes, a little over 10 per cent. A large proportion 

 of Gadow's new-born specimens came from one nest, the whole 

 brood of which was abnormal. The others were taken in small 

 sets from various collections, and I believe that such specimens 

 had been preserved because of their abnormalities. A survey of 

 my tabulations will show that abnormalities are no more common 

 in one size than in another. Finally, Coker, in a very recent 

 preliminary paper, delivered before the American Society of Zool- 

 ogists in Philadelphia, December, 1904, claims that observations 

 on embryos of TJialassochelys gave no support to the theory of 

 Gadow. 



2. Gadow considers that certain specimens (Figs. 6 and 24) 

 show evidences that the neural row was originally a double one. 

 That this was the case seems very unlikely from an examination 

 of such primitive conditions as are seen in the tail of CJielydra 

 and in the neural keel of DermocJielys. The appearances seen in 

 Figs. 6 and 24 may be due to the crowding of linear members of 

 the row until they come to lie side by side. Indications of an 

 approximation to this condition are not uncommon in the speci- 

 mens which I have had to deal with. 



