154 Field Columbian Museum — Geology, Vol. II. 



Su SD SU g§ -gu « 



2/- Sj 5£ «*> £iS 1 



gte ^ gS 85 £* 



z z z £ £ £ 



Humerus ioo ioo ioo ioo ^ioo ioo 



Ulna... 165 165 ... 136 148 153 



Metacarpal 257 275 ... 210 106 105 



First Phalange 324 327 ... 268 161 160 



Second Phalange 241 .... ... 172 142 129 



Femur 93 93 — 106 109 107 



Tibia 151 151 ... 150 153 144 



Metacarpal ' 100 100 100 — — — 



Ulna 64 60 62 



First Phalange 126 iiq 115 — — — 



It is observed that there is a striking agreement in these specimens, 

 except in the metacarpals, the differences elsewhere being scarcely more 

 than one might expect in the measurement of bones differently affected 

 by the compression to which they have been subjected. Now, we may 

 consider this variation of specific value and give to each of these three 

 specimens a different name; or we may, as is far more reasonable, 

 consider the metacarpal as a variable bone in the individual, as it is 

 in the species and groups, and refer them all to one species. This 

 I have no hesitation in doing. There is, then, but a single species 

 of Nyctosaurus now known among the specimens referred to the genus; 

 it should be called Nyctosaurus gracilis Marsh. 



In specimens of Pteranodon ingens there is not a little variation in 

 size, especially in the length of the wing metacarpal, which I have 

 observed to vary from 580 to 615 millimeters, the longest that I have 

 ever known from the Kansas chalk. It is very certain, I think, that 

 absolute identity of size cannot be relied upon to distinguish the differ- 

 ent species of pterodactyls, nor do I think that the relative or propor- 

 tional lengths of the finger bones should receive too much weight; 

 the different species evidently varied individually within certain limits. 



In my first paper on Nyctosaurus, I discussed briefly the so-called 

 species of Pteranodon, P. nanus, and P. comptus, suspecting that one or 

 both of them belonged with Nyctosaurus. 



A wider acquaintance with Kansas pterodactyls, both in the laboratory 

 and in the field strengthens my belief that both of these names are 

 synonyms of N. gracilis. 



No small species from the Kansas chalk can be referred definitely to 

 Pteranodon, so far as my own knowledge goes, and I have seen hundreds 

 of specimens. P. nanus presents the strong lateral crest of the humerus 

 which I am satisfied is a diagnostic characteristic of Pteranodon. Al- 



