513 



short dorsal branch seat backward to the dorsal tilaraents of the first 

 gill cleft would seem to represent the missing branch of the artery. 

 This is, I believe, the first time that these afierent loops have been 

 described in any fish, but as it would seem as if the condition could 

 not be limited to Chlamydoselachus alone, of all fishes, I am en- 

 deavouring to procure heads of Hexanchus and Heptanchus for special 

 examination in this respect. 



The five efferent branchial arteries of Chlamydoselachus all run 

 upward in their respective arches, as Ayers has shown them, the first 

 three emptying separately and independently into the median dorsal 

 aorta, while the last two 



unite to form a single " '.' '^ <<« 



trunk which then empties 

 into the aorta. But these 

 five arteries are, on both 

 sides of the one of my 

 two specimens, 3,bove re- 

 ferred to, that was care- 

 fully examined in this 

 respect, all connected by 

 commissural vessels, not 

 shown by Ayers, these 

 commissural vessels all 

 lying in the line pro- 

 longed of the anastomatic branch an that Ayers shows connecting the 

 hyoidean and first branchial arteries. Proximal to these commissural 

 vessels, the efferent branchial arteries all curve backward, mesially and 

 quite markedly downward to join the aorta. From each commissural 

 vessel two branches are given off', one running down on each side of 

 the related cleft, and both of them related to the gill-filament circu- 

 lation. The posterior one of these two vessels is short, and in the 

 first two arches fused ventrally with the main efferent artery. The 

 anterior vessel extends the full length of the cleft to which it is related, 

 is connected at several places by short commissure with the main 

 efferent artery of the arch, and, ventrally, turns backward around the 

 ventral end of the related cleft and becomes continuous with the ventral 

 end of the main efferent artery in the next succeeding arch; thus 

 forming an efferent loop encircling the ventral end of the cleft. The 

 anterior commissural vessel is the homologue of the posterior one of 

 the two efferent vessels usually described in each branchial arch in 

 other elasmobranchs. In the fifth branchial arch of Chlamydoselachus 



Fig. 2. Diagrammatic representation of the same. 



Anat. Anz. XXXIX. Aufsätze. 



33 



