948 DR. W. G. BIDEWOOD OiST THE [Nov.SS, 



between the first and second efferent branchial vessels is wanting, 

 owing to the backward extension of the circulus to the point of 

 entry of the second branchial vessels into the aorta. The same 

 feature is to be observed in Batistes (fig. 5), where the aortic 

 stem between the second vessel and the common trunk of the 

 third and fourth is also suppressed. The coeliaco-mesenteric artery 

 of Batistes arises, not from the aorta, but from the third and 

 fourth branchial vessels of the right side, immediately after their 

 anastomosis. 



If we disregard the modification of the efferent branchial circu- 

 lation brought about in GymnarcJms by the increased functional 

 importance of the swim-bladder, the efferent branchial system of 

 this genus can be seen, from the description and figure published 

 by Hyrtl (11. p. 11, and pi. 4. fig. 4), to conform with the type 

 which characterizes subgroup A c. 



FUETHEB EeMARKS ON GbOUP B. 



The efferent branchial system of Scomber (fig. 6) bears a close 

 resemblance to that of Salmo (fig. 7), but the coeliaco-mesenteric 

 artery arises from the aorta immediately behind the fourth efferent 

 branchial vessels and the subclavian arteries some distance farther 

 back, whereas in Sahno the positions of the cosliaco-mesenteric and 

 subclavian arteries are reversed. In the figare of Scomber given 

 by Stannius (23. pi. v. fig. 4) the circulus cephalicus appears 

 much too large, and the interval between the circulus and the 

 entry of the third and fourth branchial vessels into the aorta too 

 short. 



In Salmo trutta, as also in Osmerus and Coregonus, the dorsal 

 aorta is wide and thin-walled ; but this is not the case in Salmo 

 salar. The distance between tlie posterior angle of the circulus 

 and the point of entry of the third efferent branchial vessel is 

 pL'opoi'tionately longer in Ooregonvs than in Salmo salar, and pro- 

 portionately shorter in Salmo trutta. A very reliable figure of the 

 efferent branchial system of S. trutta has been given by Vogt 

 (1. pi. L. fig. 2). The figure by Stannius of S. salar (23. pi. v. 

 fig. 3) is incomplete, but is correct so far as it goes. In IJypo- 

 phthalmichthys both the coeliaco-mesenteric and the subclavian 

 arteries arise some distance behind the fourth efferent vessel. The 

 circulus in this genus is broader than long. 



In Hipiooglossus (fig. 9), Pleuronectes, Muc/il (fig. 8), Esox 

 (fig. 15), and Marcusenius the distance between the posterior 

 angle of the circulus cephalicus and the point of entry of the 

 common trunk of the third and fourth branchial vessels is so short 

 that these forms approach somewhat closely those included in 

 subgroups C6 and Cc. In Pleuronectes the circulus cephalicus is 

 longer than broad, whereas in Hippoglossus it is broader than long ; 

 the anterior carotids are closer together, and the transverse com- 

 missure between them is shorter than in Ilippoglossus. The 

 common trunk formed by the union of the third and fourth 

 branchial vessels of the right side is much shorter than that 



