530 6-. W. WILLI STON 



Nyctodactylus, the lesser, and Ornithostoma, the more, specialized 

 type. 



If my interpretation of the elements of the skull of Nycto- 

 dactylus is correct, I fail to see any marked avian resemblances in 

 it. The only character that might be considered as such is the 

 undivided narial vacuity, aside from the lightness of the bones 

 and their closely united sutures, both adaptive characters. The 

 supratemporal arch is purely reptilian, as is the presence of the 

 ectopterygoid, etc. The union' of the premaxillary with the 

 frontal is found in the plesiosaurs. A further discussion of this 

 question I hope to present in a future paper, in which I shall give 

 a more detailed description of the remainder of the skeleton, 

 with illustrations. 



I am convinced that the arrangement of the ribs back of the 

 sternum, not only in Nyctodactylus, but in other pterodactyls, is 

 different from what has been generally supposed and figured. 

 They extended outward in the plane of the wing membrane, which 

 they served in a measure to support, and did not enclose the 

 ventral cavity. From a recent examination of the type of 

 Rhamphorrhynchus phyllurus Marsh, I am satisfied that this was 

 their function in that animal, and I doubt not it was also in all 

 other pterodactyls. This difference in function accounts satis- 

 factorily for the marked contrast in slenderness between the 

 anterior and posterior ribs, as also for the slight curvature of 

 the latter. 



The hyoid bones of the present specimen are quite like those 

 of other pterodactyls — long, slender rods. They are shown in 

 part in Plate I. At the back of the skull in the same plate is 

 also seen a small triangular or V-shaped bone, which I take to 

 be the proatlas. 



It will be of interest to note that in the matrix underlying 

 the skull occurred several specimens of the Cirriped Stramentum, 

 together with a vivid impression of a Lepas-like barnacle having 

 a slender, flexible, naked peduncle about 40 mm in length. The 

 capitulum seems to have been enclosed either in chitinous or 

 membranous plates, evidences of which are present, and impres- 



