CHELONiA ^10 



that the rib-heads must have articulated with diapophyses. There may 

 have been some supraneurals adhering to these ribs. 



Because he found two elements which he thought (and probably cor- 

 rectly) appertained to the dermal keel that belongs above the marginal 

 bones, Wieland concluded that there were seven keels on the carapace, 

 something of a logical leap. N"ow, in case the skin was thick and 

 leathery and had lost the horny shields, how came it that the keels took 

 accurately the places of the rows of shields, just as they have done also 

 in Dermochelys. Again, if the supraneurals of Toxochelys were new 

 acquisitions, adumbrating the mosaic of Dermochelys, how came it about 

 that they at once effaced themselves by coalescing with the underlying 

 neurals? That is what we might expect from old disappearing struc- 

 tures, but not from new ones destined to play a future important role. 



As regards the classification, a few remarks may be added, especially 

 on Siebenrock's and Broili's arrangement. The remarks concern the 

 Amphichelydia, which are subordinated to the Pleurodira. However, 

 the skull presents none of the characters peculiar to the Pleurodira, but 

 is like that of the Cryptodira, with sometimes more primitive features. 

 There is no evidence that the animals protected their heads as the 

 Pleurodira do. Any Cryptodire can move its head and neck sidewise. 

 The ilia were not consolidated with the carapace. The pelvis was wholly 

 free from the shell. With the Amphichelydia included, it will be ex- 

 tremely difficult to frame a definition that will separate the Pleurodira 

 from the Cryptodira. That of Dr. Broili certainly does not accomplish 

 this. Furthermore, in case Carettochclys is referred to the Triony- 

 choidea, it will be difficult to draw the line between this superfamily and 

 the Cryptodira. The character that is of most value is apparently the 

 lack of contact between the pterygoids. 



An opportunity is here presented for some of our systematists to refer 

 Carettochelys to that ample category, the "Chelonioidea." 



BIBLIOGRAPHY 



(1) Denkschriften Museum, Solothurn, 1902. 



(2) Proceedings of the Academy of Natural Sciences, Philadelphia. 



(3) Nature, vol. Ixvi, p. .524. 



(4) Neues .Tahrbuch fiir Mineralogie. Geologic und Palaontologie, Stuttgart. 



(5) Bollettiuo Societa Zoologica Italiana. 

 (G) Bollettino Societa Zoologica Italiana. 



(7) Issued at Reggio, Calabria. 



(8) Rivista Italiana di Paleontologia. 



(9) Canada Geological Survey, Summary Report. 



(10) American Jouraal of Science. 



(11) Survey Department, Public Works Ministry, Cairo. 

 JCVI— Bull. Gbol. Soc. Am., Vol. 23, 1911 



