On (he Anatomy o/'Eryx and other Boida?. 233 



keeled. Areola sligLtly wider than long, rounded at the 

 base, the apex bulging inwardly; the base of posterior 

 median area smooth, the rest transversely striated ; the outer 

 apical arese are more strongly and widely striated. The 

 upper half of propleurse closely punctured, as are also the 

 mesopleurse; the metapleurse are more closely and strongly 

 punctured. First segment of abdomen aciculated, the post- 

 petiole more strongly and raised in the middle ; the second 

 and third segments are closely punctured; the gastroccsli 

 wide, striated, the oblique apex aciculated. 



XXIV. — Preliminary Note on certain Points in the Anatomif 

 of Eryx and other Boiclte, partly indicative of their Basal 

 Position among the Ophidia. ]3y Feank E. Beddard, 

 M.A., F.R.S. 



It is generally believed that the Boidje occupy phylo- 

 genetically a ph^ce at or near the. base of the Ophidian series ; 

 and this view is expressed by Boulenger in a tabular state- 

 ment of the mutual affinities of the various families of the 

 Order *. This opinion is largely based upon the persistence 

 of considerable vestiges of the pelvic girdle and upon the 

 paired lungs. In studying the anatomy of snakes I have 

 been able to note a few other points to which little or, in 

 some cases, no attention has been paid and which tend to 

 the support of this conclusion. My observations bearing 

 upon this subject were made upon Python, Eryx, and Boa. 



The first point to which 1 would draw attention is the 

 equal size of the right and left aortic arches, w^hich join to 

 lorm the dorsal aorta. In at least many other snakes (for 

 example, Zamenis fagelliformis) the right aortic arch is so 

 much the smaller that it appears almost as an inconspicuous 

 branch of the left. It would appear, however, that in Python 

 hivittatus this is not the case f, though Dr. Gadow's drawing J 

 of Pelophilus madagascariensis is in accordance with the facts 

 which I have observed. 



Secondly, the intercostal branches of the aorta are arranged 

 in a fashion which appears to me to be distinctly archaic. 

 In most snakes the intercostal arteries are very irregular in 



* 'Catalogue of the Snakes in the British Museum (Natural History),' 

 London, 18U3, vol. i. p. 2. 



t Jironn's ' Klassen und Ordnungen des Thierreiclis,' Bd. vi. Abth. iii, 

 pi. cxxxiv. fig. 2. This figure is copied from Frit.-jch. 



I ibid. pi. c.\xxv. fig. 1. 



