332 BIR. F. E. BEDDARD OX THE [Feb. 16, 



snakes what Hopkinson and Pancoat * and (moi-e recently as well 

 as more thoroughly) Jacqnai't t have attempted in the Python, 

 and GadowJ in Felop}dlus madagascariensls. hut with more, 

 descriptions of certain details. 



Table or Contexts. 



Zanienis mucosus, p. 332. Corojiella fjetida. p. 352. 



Zamenisflagelliformis, p. 338. j Ophiopliagus huiigarus. p. 355. 



Zanienis gemonensis, p. 341. | Naia tvipudians, p. 359. 



Coluber catenifer, p. 342. j Fi/thon spilotes, p. 362. 

 Coluber melanoleucus, p. 344. Lachesis gramineus, p. 366. 



Tropidonotusfasciatus, p. 346. Some General Conclusions, p. 368. 



Zamenis mucosus. 



Intercostal Arteries. — Snakes of this species show a more marked 

 disproportion between the right and left aoi-ta than in the case 

 of Z . JJagelUformis. The diameter of the left aorta at the point of 

 junction is as nearly as possible 6 mm. ; the right aortic at its 

 junction with the left measures barely 2 mm. The left aortic arch 

 gives off no intercostals ; f i-om the right ai-ise foui-, which correspond 

 to successive vertebrae and ai'e therefore close together, leaving a 

 gap posteriorly where there are no intercostals. The first of these 

 arises from the aorta just after it has left the common trunk ; the 

 second divides early into two vessels which enter the body- wall 

 side by side ; the same is the case with the fourth vessel, but its 

 two branches are here of unequal size. The third vessel at least, 

 if not the others, gives off a branch to the cesophagus. In theii- 

 bifurcation, and by reason of the fact that they give off branches 

 to the oesophagus, these intercostals resemble those which arise 

 from the anterior vertebi-al artery. Behind the junction of the 

 two aortas the intei-costals are rather different. They may be 

 divided into an anterior and a postei'ior series, the difference beiiag 

 that those of the anterior series are irregular while those of the 

 posterior series are regularly intervertebral. They are further- 

 more not concerned with the blood-supply of the cesophagus, the 

 latter being supplied from special trunks arising separately from 

 the aorta. There are 16 intercostals § belonging to the anterior 

 series, which ends at the level of the gall-bladdei-. The numbei- 

 of vertebrae lying between the points of entrance into the parietes 

 of the sviccessive arteries is as follows : — 



I. 8, II. 5, III. 4, lY. 3, Y. 2, YI. 4, YII. 6, YIII. 5, IX. 5, 

 X. 3, XI. 2, XII. 2, XIII. 3, XIY. 1, XY. 2, XYI. 2, 

 XYII. 1, XYIII. 1, &c., &c. 

 Xearly all of these arteries enter the body-wall to the left of 



* '•' On tlie Visceral Anatomy of the Python (Cuvier) described by Daudin as the 

 Boa reticulata" Trans. Am. Phil. Soc. \. 1837, p. 121. 



t "Memoir siir les Orgaues de Circulation chez le Serpent Python,"' Ann. Sci. 

 Nat. (4) iv. p. 321. 



X Incorporated in Bronn's ' Thier-Eeich,' loc. cit. 



§ Perhaps 17 should be assigned to the anterior series. 



