1899.] BLOOD-TESSELS OF TELEOSTEAN FISHES. 949- 



on the left, and the origin of the coeliaco-mesenteric artery is 

 nearer the middle line than in Bippoglossus. In Mugil (fig. 8) 

 the cireulus cephalicus is considerably longer than broad, and 

 the cceliaco-mesenteric artery arises from the median aorta behind 

 the entry of the third and fourth branchial A^essels, and not as in the 

 two preceding genera. In Osmerus (fig. 10) and Alhida (fig. 11 ), 

 also, the coeliaco-mesenteric artery arises from the median aorta, 

 but the subclavian arteries take their origin immediately behind 

 the point of entry of the common trunk of the third and fourth 

 branchial vessels iuto the aorta, and not behind the coeliaco-mesen- 

 teric artery as in Mugil. 



In Scopelus the cireulus cephalicus is small and nearly circular 

 in shape, and the portion of median aorta intervening between its 

 posterior angle and the mesial ends of the common trunks of the 

 last two branchial vessels is unusually long. In Malapterurus 

 (fig. 12) and Esox (fig. 15) the coeliaco-mesenteric artery arises 

 from the aorta immediately ventral to the mesial ends of the 

 common trunks of the third and fourth vessels; in Cyprinus 

 (fig. 13), Cobitis (&g. 14), and Ilarcusenius it arises more posteriorly, 

 and in AnguiUa (fig. 16) considerably farther back. Except in this 

 latter respect, the arrangement of the vessels in Marcusenius very 

 closely resembles that of Esox. 



Judging by the excellent figure of Tinea published by Hyrtl 

 (7. pi. iv.), this genus exactly resembles Cypriuus in the dispo- 

 sition of the vessels of the efferent branchial system. The efferent 

 vessels of Cyprinus were figured by Duverney (6. pi. ix. figs. 17 

 & 18) nearly 140 years ago ; and although the figures are in- 

 complete, the essential features are correctly represented. In Cypri- 

 nus, and according to Hyrtl in Tinea also, there are two pairs 

 of subclavian arteries. The anterior pair, arising in front of the 

 common trunks of the last two branchial vessels, supply the upper 

 part of the pectoral arch, the posterior pair the lower part of the 

 arch and the pectoral fins. A somewhat similar arrangement obtains 

 in Esox. The mode of origin of the anterior pair has been re- 

 marked by Midler, and quoted by Stannius (22. p. 103, footnote 3) 

 and Owen (18. p. 270, and 19. p. 489), and these vessels are shown, 

 although not named, in Maurer's figure (13. pi. xi. fig. 1). 



The cireulus is large in Malapterurus and AnguiUa ; and in the 

 latter genus a median vessel, occupying the position of the anterior 

 continuation of the primitive median aorta described in Selachian 

 fishes by Ayers (4), may be traced forward from the posterior 

 angle of the cireulus. It soon forks, and is ultimately lost in the 

 mucous membrane of the roof of the pharynx. In AnguiUa, also, 

 the origin of the posterior carotid artery is much farther removed 

 from the entry of the first branchial vessel into the cireulus than 

 is usual. Meckel has stated (14. p. 193) that in the marine Eel, 

 Miircenophis helena (Murcena helena), the anterior lateral trunk 

 formed by the union of the first and second branchial vessels is 

 three times as long as the posterior one formed by the union of 

 the third and fourth. 



