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Show 332 MR. F. E. BEDDARD OX THE [Feb. 16, snakes what Hopkinson and Pancoat * and (more recently as well as more thoroughly) Jacquartt have attempted in the Python, and GadowJ in Pelophilus madagascariensis, but with more descriptions of certain details. TABLE OF CONTEXTS. Zamenis mucosus. p. 332. Coronella getula, \>. 352. Zamenisfiagelliformis, p. 338. Ophiophagus bungarus, p. 355. Zamenis gemonensis, p. 341. Naia tripudians, p. 359. Coluber catenifer, p. 342. Python spilotes, p. 362. Coluber melanoleucus, p. 344. Lachelis gramineus, p. 366. Tropidonotas fasciatus, p. 346. Some General Conclusions, p. 36S. ZAMEXIS MUCOSUS. Intercostal Arteries.-Snakes of this species show a more marked disproportion between the right and left aorta than in the case of Z.fagelliformis. The diameter of the left aorta at the point of junction is as nearly as possible 6 m m . ; the right aortic at its junction with the left measures barely 2 m m . The left aortic arch gives off no intercostals ; from the right arise four, which correspond to successive vertebra? and are therefore close together, leaving a gap posteriorly where there are no intercostals. The fiist 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 oesophagus. In their bifurcation, and by reason of the fact that they give off branches to the oesophagus, these intercostals resemble those which arise from the anterior vertebral artery. Behind the junction of the twro aortas the intercostals are rather different. They may be divided into an anterior and a posterior series, the difference being that those of the anterior series are irregular while those of the posterior series are regularly intervertebral. They are furthermore not concerned with the blood-supply of the oesophagus, 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-bladder. The number of vertebrae lying between the points of entrance into the parietes of the successive arteries is as follows :- I. 8, II. 5, III. 4, IV. 3, V. 2, VI. 4, VII. 6, VIII. 5, IX. r>. X. 3, XI. 2, XII. 2, XIII. 3, XIV. 1, XV. 2, XVI. 2. XVII. 1, XVIII. 1, Ac, &c. Nearly all of these arteries enter the body-wall to the left of * "On the Visceral Anatomy of the Python (Cuvier) described by Daudin as the Boa reticulata" Trans. A m . Phil. Soc. v. 1837, p. 121. t "Memoir sur les Organes de Circulation chez le Serpent Python," Ann. Sci. Nat. (4) iv. p. 321. X Incorporated in Bronn's ' Thier-Reich,' loc. cit. § Perhaps 17 should be assigned to the anterior series. |
