710 ntOF. OWEN ON THE RANK AND AFFINITIES IN 



of a vertebra from the same (fore) part of the spinal column in an 

 Iguana (fig. 22) and a Python (fig. 24). In the two latter the parts 

 are symbolized by the same letters as in the monograph above cited, 

 viz. : — c, centrum (anterior surface or cup) ; », neural canal ; c?, dia- 

 pophysis ; z, praczygapophsis ; zs, zygosphene ; n s, neural spine ; liy, 

 hypapophysis, with, in the Lacertian (fig. 22), the autogenous ap- 

 pendage marked hs, as representing a haemal spine. The corre- 

 sponding letters are added to the homologous parts in the figure (fig. 

 23) from Cope ; but I find no place for zs in that figure. 



As the absence of a sacrum does not affect the Mammalian grade 

 of the Sirenia and Cetacea, so neither does it the Lacertian nature 

 of the Mosasaurians. That negative character is of as little value in 

 an advocacy of the Ophidian affinities of the Ichthyo- or Plesio- 

 saurians, as of the same affinities of the Mosasaurians. 



§ 9. Limbs. — The determinations by Cuvier of certain bones and 

 portions of bone in the original Camperian collection of remains of 

 the Maestricht Mosasaur as scapula, coracoid, pubis, antibrachial, 

 carpal, and phalangeal bones *, established the capital fact that it 

 was a reptile with both scapular and pelvic arches, and their 

 appended limbs. Evidence had been obtained at the date of the 

 * Bridgewater Treatises ' to enable Buckland to define these limbs 

 as " flippers," like those of the Plesiosaur. 



The subsequent discoveries of Professors Cope f and Marsh J have 

 confirmed these determinations, and extended our knowledge of the 

 nature of the limbs as natatory ones, and with phalanges manifesting 

 the proportions of those of the Plesiosaurs and sea-Chelonians rather 

 than of the Ichthyosaurs. But the number of digits in each limb 

 and of the phalanges in each digit remain to be determined. 



Sternal or episternal elements of the scapular arch seem not to 

 have been recognized in the American series of fossils ; but ample 

 evidence has been secured of those parts of the frame of the Mosasau- 

 rians which bear decisively on the question of their rank, position, 

 and affinities in the Keptilian class. 



Professor Cope, in support of his proposition that the Mosasauroids 

 " present more points of affinity to the serpents than does any other 

 order" §, on which proposition he founds his name Pythonomorpha, 

 accepts the fact of their well-developed limbs by the following 

 remark. : — " As there are many Lacertilia without limbs and some 

 serpents with them, their presence in this order is irrelevant in this 

 connection, especially as the arches supporting them are most like 

 those of Tortoises and Plesiosaurs " || . But supposing, which is not 

 the case, that the scapula of Mosasaurus was like that of a Tortoise 

 or a Plesiosaur, Serpents have not got such scapula or any other ele- 

 ment of the limb-bearing arches. 



* Tom. cit. p. 336. pis. xix., xx. 



t Proceedings of the Boston Society of Natural History, January 1860, p. 250 

 (scapular arch and fore limb). 



\ American Journal of Science and Art, June 1871, p. 472 (pelvis and hind 

 limbs). 



§ Op. cit. p. 126. || Ibid. p. 115. 



