The Anatomy of Chlamydoselachus 



461 



br.af 



are four transverse rows with at least three valves in each row — the precise number is 

 uncertain. The same may be said of No. I. 



As stated by Garman (1885.2), generally among sharks the conus is shorter and the 

 transverse rows of valves less numerous, than in Chlamydoselachus. In Carman's Pis. 

 56 and 57 (1913) we find illustrated (without text) the external form of the heart, and 

 the form and arrangement of the valves of the conus arteriosus, in many different species 

 of elasmobranchs. The heart of Heptanchus maculatus (Text-figure 104a) has a fairly 

 long conus arteriosus — longer than that of Hep- hy af., 

 tranchias {Heptanchus) perlo (Garman, 1913, Fig. 

 1, pi. 56) but shorter than that of Chlamy- 

 doselachus. In Heptanchus (Text'figure 104b) 

 the valves of the conus arteriosus show partial 

 suppression of the second row counting from the 

 distal end of the conus, and complete suppression 

 of the third row. 



THE BLOOD VESSELS 



For descriptions of the blood vessels of 

 Chlamydoselachus, we must rely almost entirely 

 on the work of Ayers (1889) and Allis (1908, 1911, 

 1912 and 1923). In several respects, the condition 

 of the arteries as described and portrayed by 

 Ayers is not typical for Chlamydoselachus. His 

 work has been severely criticised, but in view of 

 the marked variability that has been found in 

 other organs and parts of Chlamydoselachus, it 

 seems possible that he worked on an anomalous 

 specimen. I have included two of his figures 

 (Text'figures 105 and 106), because of their his- 

 torical importance and because they are more 

 comprehensive than those of other authors. 



Text-figure 104. 



Ventral views of (A) heart and ventral aorta, 



(B) valves of the conus arteriosus, 



in Heptanchus maculatus. 



dp., aperture of last afferent artery; au., auricle (atrium); 

 hr.af.l-6, first to sixth afferent branchial arteries; 

 c.a., conus arteriosus; ct.I., left coronary artery; hy. aj., 

 afferent hyoidean artery; p.c, pericardial artery; v.a., 

 ventral aorta; v.c, valves of the conus; tin., ventricle. 

 From Daniel, 1934, Fig. 150a and b; the latter redrawn 

 after Garman, 1913, Fig. 1, pi. 59- 



THE ARTERIES 



In Chlamydoselachus, particular interest attaches to the study of the dorsal aorta 

 (anterior portion), the branchial arteries, and the circulation within the gills. 



The Dorsal Aorta. — Ayers (1889) described a slender median artery, coursing 

 in the basis cranii, which he called the cranial aorta (c in Text-figures 105, 106, and 22 

 p. 352) since he regarded it as a direct continuation of the dorsal aorta. "Unlike all 

 other gnathostomous vertebrates, Chlamydoselachus has a dorsal aorta (dorsal vessel) 

 running the entire length of the notochord, to which it is intimately attached throughout 



