406 MR. B. W. HOOLET OS THE [June I913, 



Prof. S. W". Williston 1 as found in the inner angle of the fused 

 bones enclosing a foramen. He mentions, too, that a similar process 

 and foramen are seen in a Cambridge Greensand example described 

 by Owen, 2 who assigns this girdle to Pterodactylus sedgividci (syn. 

 OmithocJieirus sedgivichi Seeley sp.). Dr. Plieninger 3 also notes its 

 occurrence in Pt. suevicus. The foramen seen in these specimens is 

 clearly the remnant of a cleft that once existed between this process 

 and the girdle, and there is much to be said for Prof. "Williston's 

 suggestion that it is ' possibly a vestigial clavicle.' If I under- 

 stand correctly, the line of union between the scapula and the 

 coracoid in Omitliostoma runs horizontally across the glenoid cavity. 

 In that respect it is similar to Ornithodesmus and Nyctosaurus, and 

 different from both these in the line being transverse and like a 

 Cambridge Greensand example figured by H. G. Seeley. 1 



The Humerus. 



The great development and spiral curve of the deltoid crest 

 distinguishes Ornithodesmus from all other genera. The only 

 humeri that I can discover which have a somewhat similar spiral 

 curve, although in not so great a degree, are those from the Lower 

 Chalk of Bluebell Hill, Burham (Kent), in the British Museum 

 (Natural History), and numbered respectively B/1935 and K/1357. 

 The very high specialization of the distal end cannot be compared 

 with that of any known genus. The distal end of a humerus R/37 

 in the same Museum approximates to it. Distal ends of humeri 

 from the Cambridge Greensand, in the Sedgwick Museum, show 

 it in an incipient degree. The German forms, where the distal 

 end can be examined, possess a trochlear joint with the radial 

 condyle greater than the ulnar. 



The large circular foramen on the articular surface of the distal 

 end of the humerus of Ornithodesmus is certainly very curious. 

 Possibly a synovial gland was located here. It is represented by a 

 pit or depression in Omithostoma. 5 



The Radius. 



The remarkably reduced dimensions of the radius, when com- 

 pared with the ulna, form a unique character. It is an interesting 

 parallel modification with birds. The proximal articulation is 

 more specialized, and consequently differs from the simple and 

 almost flat articular face of the proximal end of the radius in 



1 ' Osteology of Nyctosaurus {Nyciodactylus), &c.' Field Col. Mus. Publ. 78, 

 Geol. Ser. vol. ii, No. 3 (1903) p. 140; also 'Eestoration of Omithostoma 

 (Pteranodon)' Kansas Univ. Quart, ser. A, vol. vi (1897) p. 43. 



2 ' Foss. Eept. Cret. Form. ' (Monogr. Pal. Soc.) 1859, Suppl. i, p. 14. 



3 ' Pterosaur, d. Jura Scbwabens ' Palseontograpbica, vol. liii (1907) p. 268. 

 * 'The Ornithosauria ' 1870, pi. i, fig. 10. 



5 S. W. Williston, ' Osteology of Nyctosaurus (Nyctodacfylus), &c.' Field. 

 Col. Mus. Publ. 78, Geol. Ser. toI. ii, No. 3 (1903) p. 142. 



