MORPHOLOGY AND MATHEMATICS. 



883 



In my figure I have completed this missing part of the bone in harmony with the 

 general co-ordinate network which is suggested by our comparison of the two entire 



Fig. 42. — Pelvis of Steyosaurtis. 



Fig. 43. — Pelvis of Camptosaurus. 



pelves ; and I venture to think that the result is more natural in appearance, and 

 more likely to be correct than was Marsh's conjectural restoration. It would seem, 

 in fact, that there is an obvious field for the employment of the method of co-ordinates 





























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a. b. 



FrG. 44. — Shoulder-girdle of Cryptodeidus. a, young ; b, adult. 



Fig. 45. — Shoulder-girdle of Ichthyosaurus. 



in this task of reproducing missing portions of a structure to the proper scale and 

 in harmony with related types. To this subject we shall presently return. 



In fig. 44, a, b, I have drawn the shoulder-girdle of Cryptodeidus, a Plesio- 

 saurian reptile, half-grown in the one case and full-grown in the other. The 

 chano-e of form during growth in this region of the body is very considerable, and 



