RESTORATIONS OF PTERANODON. 37 



over the dorsal region, is most striking. And the appearance of the hind limbs in the 

 complete restoration well sustains the truth of Professor Seeley's contention that the 

 " slender toes of many bird?, and even the two toes of the ostrich, may be thought to 

 give less adequate support for those animals than the metatarsals and digits of Ptero- 

 dactyles." The small size of the pelvis compared with the rest of the skeleton will at 

 once arrest the attention of a biologist in whose mind the question arises how the 

 females of this genus could have produced their young. Were it not for the greatly 

 elongated wings and the supraoccipital crest, the pelvic diameters would not seem so 

 disproportionate ; for compared with the size of the thorax of the adult animal, the 

 channel enclosed by the ischio-pubes is not relatively much smaller than that observed 

 in some of the Crocodilia and Chelonia. That this character is perhaps a little more 

 pronounced in Pteranodon than in the earlier pterosaurs, need cause no surprise, inas- 

 much as Pteranodon is in nearly every respect more specialized than the other genera. 

 The seemingly immoderate proportions of the head and wings were probably due en- 

 tirely to postnatal growth ; and while difficulty of parturition might ultimately have 

 become a factor in exterminating the genus, it should be remembered that the pro- 

 portions of the axial skeleton and limb girdles figured in the restorations are taken from 

 well-preserved specimens and therefore can not be regarded absurd. There is as yet 

 no definite evidence to show whether the animals were viviparous or produced soft- 

 shelled eggs. 



Like many another extinct group of American vertebrates described as being of " gi- 

 gantic size," Pteranodon seems in this respect to have surpassed its Old- World congeners. 

 The wing-spread of any example a dimension that perhaps conveys a more definite idea 

 of size than do other measurements - - may be calculated by assuming that the wing 

 bones missing in any individual were of average proportions, and by computing their 

 lengths from the averages given in Table B ; but it is obvious that the resultant calcu- 

 lation is approximate only. Allowance must also be made for the diameter of the thorax 

 and for the carpus. Contrary to precedent, the wing-spread is here estimated as the 

 distance from the tip of one terminal phalanx to that of the opposite limb, with all the 

 joints slightly flexed, especially the elbow and the carpus, this position of the wings 

 affording a more natural measurement than the total length of the same bones stretched 

 in a straight line from shoulder to wing-tip, although by the latter method the size would 

 be made to appear about five per-cent. greater. 



The wing-spread of several of the examples referred to in the foregoing pages may 

 be approximately stated, as follows : - 



m. ft. in. 



No. 1164, type of P. occidentals 3.855 = 12 8 



No. 1175, type of P. ingens 6.803 = 22 3 



No. 2493, Pteranodon sp 4.902 = 16 



No. 1181, Pteranodon sp 3.390 = 11 1 



The wing-spread of the type of P. longiceps, No. 1177, was probably nearly equal to 

 that of No. 2493; the type skull of P. occidentalis, No. 1179, belonged to an individual 

 of about the same size as No. 1164, while the two types of P. inyens, Nos. 1175 and 

 2594, apparently had about the same wing-spread. Perhaps the largest example of Pteran- 

 odon sp. in the Marsh Collection is No. 2514, represented by the right quadrate and 

 the proximal ends of the radius and ulna. The quadrate exceeds in size that of P. ingens, 

 No. 2594, by one-fifth. If this proportion remained constant throughout the entire skeleton, 



