304 On the Skeleton of iSTyctodactyhis, with Eestoration 



later forms and the greater 23rop*ortioual development of the middle 

 fingers in the early forms, the end of the thnmb was drawn backward 

 and rendered tense, nntil finally its position became directly opposite 

 to the original one. 



AVe must assume then that the membrane originally was developed 

 to a greater or less extent in front of the arm as well as behind it. Had 

 the membrane finally disappeared here, it is only natural to suppose that 

 the bone controlling it would become vestigial — assuming Lamarckian 

 views! On the contrary, it has evidently increased in size, for it seems 

 to be larger in this one of the most specialized of all pterodactyls than in 

 the earlier ones. What then could be its functions, unless as the sup- 

 port of a membrane that extended over the shoulder to the sides of the 

 neck? I can not say that I am convinced that this really was the case 

 in our Nyctodadylus, but I think it not improbable. 



The attachment of what I believe to be the pectoral muscles was by a 

 stout and prominent process on the inner proximal side of the humerus.^ 



In an earlier communication I stated that the upper part of the bill or 

 beak in Ornithostoma was not produced in a sharp ridge as Marsh stated, 

 but that it was rounded. Plieninger (1. c), however, thinks that I was 

 mistaken and that Marsh was right. " Die Medianlinie des Schadels ist 

 im vorderen Theile in eine scharfe Kante ausgezogen, welche allmahlich 

 nach hinten, gegen die Xasopra?orbital Offnung hiu, in eine sanfte, 

 stumpfe Eundung iibergeht; allem Anscheine nach ist die scharfe Kante 

 im vordersten Theile nicht durch Druck hervorgerufen, sondern war ur- 

 spriinglich vorhanden." In the present specimen the skull is in a most 

 admirable state of preservation, and an examination of it proves beyond 

 shadow of doubt that the median part above was roundly, evenly and 

 smoothly convex, at least as far back as the narial opening. " Die 

 Oberflache der Schadelknochen ist fast durchwegs mit verschicden ge- 

 formten, meist anuahernd ovalen Griibchen bedeckt. Williston glaubt, 

 dass nur der Abdruck der in der spongiosen Masse befindlichen Hohl- 

 raume sei, eine Ansicht, welche ich nicht theilen kann.'' — Plieninger 

 (1. c). The upper surface of the beak does not show the slightest indi- 

 cations of such depressions, but is perfectly smooth and plane. This 

 condition I have seen so often in OrnWiostoma that I feel sure that the 



^Plieninger rightl}' objects to the use by me of tbe term "bicipital crest" for 

 this process, by saying that it was not for the attachment of the biceps muscle, 

 wliich never arises from the humerus. That so unpardonable an error may not be 

 attributed to one who has taught human anatomy for many years, I may say that I 

 used the term, inadvertently, in the anthropotomic sense of the " anterior bicipital 

 ridge " and as such I believe it to be correct, though not a proper term here. 



