703 



points where six consecutive points of the curve lie in a conic. In 

 the particular case where the given curve is a cubic, the last-men- 

 tioned species of singular points have heen considered by PKicker 

 and Steiner, and in the same particular case, the theory of the conic 

 of five-pointic contact has recently been established by Mr. Salmon. 

 But the general case, where the curve is of any order whatever, has 

 not, so far as I am aware, been hitherto considered ; the establish- 

 ment of this theory is the object of the present memoir. 



II. "On the Vertebral Characters of the Order Pterosauria (Ow.) 

 as exemplified in the Genera Pterodactylus (Cuv.) and Di- 

 morphodon (Ow.)." By Professor OWEN, F.R.S. &c. Re- 

 ceived February 23, 1859. 



(Abstract.) 



After mentioning various considerations which have tended to 

 invest the question of the vertebral characters of the Pterodactyles 

 with peculiar interest ; above all, in reference to carrying out the 

 comparison of their skeleton with that of birds ; the author alludes 

 to the scanty information on the subject already on record, which 

 with the exception of a remark of Professor Quensted as to the 

 apparently procoelian characters observed by him in a dorsal ver- 

 tebra of Pterodactylus Suevicus, and the apparent want of the 

 trochlear form in the cervical articulations of that animal affords no 

 available data for comparing the vertebral mechanism of these rep- 

 tiles with that of other vertebrata adapted for flight; he then 

 gives a summary of his own observations, made, as opportunities 

 presented themselves, for some years past. 



From investigations of species of Pterosauria extending from the 

 period of the Lias, as exemplified by the Dimorphodon macronyx, to 

 the upper green-sand, as exemplified by the Pterodactylus Sedgwickii 

 and Pter. Fittoni, the author has ascertained the fact, that, with 

 respect to the cervical and dorso-lumbar vertebrae, the terminal ar- 

 ticular surfaces of the vertebral bodies are simply concave anteriorly 

 and convex posteriorly, and that they consequently manifest the 

 earliest known instance of the " procoelian " type which now pre- 

 vails in the reptilian class. But in no other reptile are those arti- 



