"ABNORMALITIES IN CHELONIA. 95 



present paper it has been shown that there is no ontogenetic con- 

 nection between the scutes and plates, the former being laid down 

 before the latter have begun to form, while the latter appear com- 

 paratively late in development as mere outgrowths of the ribs 

 and neural spines. 



If, however, there be any essential connection between these 

 scutes and plates, we would expect to find scute irregularities and 

 abnormalities associated with plate irregularities and abnormalties 

 and vice versa. 



G. H. Parker ('99) expresses himself at some length on this 

 point in a paper entitied " Correlated Abnormalities in the Scutes 

 and Bony Plates of the Sculptured Tortoise." He describes in 

 detail two abnormal specimens and on this slender basis reaches 

 some rather general conclusions. 



Specimen no. i has extra eighth and tenth neurals and a small 

 right tenth costal. No plate abnormalities are found in the neu- 

 rals or costals, but one right marginal plate and a correspond- 

 ing scute are lacking. Parker designates these conditions as : 

 (a) Scute abnormalities unassociated with plate abnormalities, ($) 

 scute abnormalities associated with plate abnormalities. 



Specimen no. 2 has normal neural and costal scutes, but lacks 

 an entire horizontal row of plates consisting of a neural, a pair of 

 costals and a pair of marginals. The lack of marginal plates is 

 associated with the lack of a corresponding pair of scutes. These 

 conditions are designated as : (rt) Plate abnormalities unassociated 

 with scute abnormalities, and (//) scute abnormalities correlated 

 with plate abnormalities. Parker finds the second specimen 

 shorter than the average normal specimen of the same sex in the 

 proportion of 1.298 to 1.313. This is due to the loss of a verte- 

 bra and pair of ribs. 



In both cases it will be seen that the only real correlation 

 occurs in the marginals and that here the correlation is perfect. 

 Another correlation not mentioned by the author is seen in the 

 second specimen, where there is a reduction of marginals in sym- 

 pathy with the reduction in neurals and costals. This correla- 

 tion is, I believe, of a different sort from that seen in the marginal 

 plates and scutes, in that a common cause has brought out the 

 same general effect in both sets of structures. In both cases of 



