"ABNORMALITIES IN CHELONIA. IO5 



margin of the fourth scute. The fifth scute is a supernumerary 

 neural (No. 8) and hence the occurrence of an ossicle at its keel 

 shows that it belongs in the neural row in spite of the fact that 

 it is crowded to one side. All of the ossicles are imbedded or 

 inlaid in the centers of certain of the neural plates. If they 

 were merely the loosened centers of these plates, we would 

 surely expect to find them on all the plates instead of just 

 those which lie beneath the keels of the scutes. In what respect 

 do these ossicles, then, differ from those seen in Toxochelys 

 serrifcr by Hay ? Merely in this, that they are much reduced in 

 size, so that each is confined to one neural plate, extending back 

 so as to overlap the anterior portion of another plate. 



The specimen is an oddity in many respects. It is unusually 

 long in the carapace ; possesses fifteen plates in the neural row 

 instead of the normal number,, twelve (three of these probably 

 representing supernumerary procaudals) ; two extra costal plates 

 or ribs, one quite vestigial ; two supernumerary scutes of large 

 size ; one supernumerary costal scute of large size on the right 

 side ; and two well-developed supernumerary inframarginals on 

 each side. Other minor peculiarities might be noted, but they 

 do not concern the carapace or plastron. All of the anomalies 

 mentioned may be viewed as of atavistic character, and it should 

 not be surprising to find that the curious specimen shows an even 

 more significant atavistic recurrence than any other specimen thus 

 far examined, namely, a reversion to the condition seen in Tox- 

 ochelys. That the genus Grapteinys originally possessed a me- 

 dian dorsal keel composed of prominent bony tubercles covered 

 with chitinous sheaths (scutes) is rendered extremely probable 

 when we examine the young, especially that of G. pseudogco- 

 grapJiica, a specimen of which is pictured in Agassiz' Contribu- 

 tions to the Natural History of the United States, Vol. II., Plate 

 II., Figs, ii and 12. This specimen, which may perhaps be an 

 extreme type, although Agassiz does not suggest that such is 

 the case, shows a series of three very remarkable dorsal tubercles 

 on the second, third and fourth scutes. These tubercles furnish 

 a close approximation in general form to those seen on the tail of 

 Chclydra. It will be noted that these tubercles occur exactly in 

 the places where I have found the vestigial ossicles in a specimen 



