G. R. Wieland — On Marine Turtles. 97 



With respect to the distal phalanges of the fourth and fifth 

 fingers, it should be stated that the present restoration is of 

 necessity more or less generalized. These phalanges being 

 more slender than those of the first and second fingers, have 

 suffered crushing, and having been isolated also, one cannot be 

 wholly sure of their exact order. Nevertheless, it is fully 

 evident that fingers 8-5 are long, and have the structure seen 

 in strictly marine turtles. In the appended table of measure- 

 ments only those elements are given which may be determined 

 with reasonable certainty, though the estimated lengths of 

 fingers 3-5 are doubtless very near the truth. 



At least we are enabled to deduce tlie principal variants in 

 the evolution of the Testudinate fiipper from some generalized 

 type of foot like that of Chelydra. The humeral changes in 

 general form I have already outlined at some length. In the 

 case of the remaining elements it would of course be desirable 

 to consider an approximately phyletic series, but in the absence 

 of this, the general trend of change may best be made clear by 

 considering the percentage of length of the elements of the. 

 flipper in Chelydra^ Toxochelys^ EretmoGhelys and Derino- 

 chelys. These are, together with Acichelys of the Jurassic, 

 and the known portions of Archelon, as follows : 





g 



CO 





<D 



to 



- 



:: 



- 







CD 



^ 





p3 









o 





B 



pi 



'i 



3 





^ 



^ 



^ 



:3 is 





ffi 



K 







m 



^ 



o3 



■^ 



lO P-i 



Dermochelys, 



100 



43 



39 



127 



180 



209 



173 



86 23 



Erefmochelys, 



100 



58 



44 



49 



89 



128 



105 



44 12 



Archelon, 



100 



54 



51 



















— 21 



Toxochelys, 



100 



58 



50 



51 



78 



100 ± 



104 ± 



70 ± 11 



Chelydra, 



100 



52 



53 



50 



72 



73 



55 



50 (small) 



Acichelys 



















(=Eurysterinim), 



100 



57 



51 



40 



54 



68 



66 



51 17 



Inspection of the above table shows : 



1. Strongly marked radial and ulnar decrease in length. 



2. Greater or less elo7igation of the radius as compared loith 

 the xdna. 



3. Nearly static length of the first finger in the Chelonidaii 

 forms., with sharp increase in Dermochelys. 



Jf. Persistent increase in the length of fingers 2-]/.. 



5. More or less variable tendency to increase in length of the 

 Hfth finger. 



6. Great pisiform increase, lohich began relatively early. 



