946 DE. W, G. EIDEWOOD ON THE [NoV. 28, 



fall definitely into the one or the other subgroup. "Without this 

 subdivision, such remarkably different forms as Anarrlnchas 

 (jSg. 23) and Trigla (fig, 28) would come under the same heading. 



CLASSinCATION OF THE GrEIirEEA EXAMINED. 



Group A. The first efferent branchial vessel opens into the 

 eirculus cephalicus, but the second does not. 



Subgroup a. The third and fourth vessels open into the 

 median aorta separately. — Engraulis (fig. 1). 



Subgroup b. The third and fourth vessels open into the 

 median aorta together. — Clupea (fig. 2), Ammoch/tes 

 (fig. 8). 



Subgroup c. The third and fourth vessels on each side 

 unite to form a common trunk, which reaches the 

 aorta some distance behind the second vessel. — 

 Chirocentrus, Megalops (fig. 4). 



Subgroup d. The third and fourth vessels on each side 

 unite to form a common trunk, which reaches the 

 median aorta immediately behind the second vessel. — 

 Baltstes (fig. 5). 



Group B. The first and second efferent branchial vessels open 

 into the eirculus cephahcus, and the third and fourth into 

 the median aorta at some distance behind the eirculus. 



Subgroup a. The third and fourth vessels open into the 

 aorta together. — Scomber (fig. 6), Hypophthalmichtliys, 

 Salmo (fig. 7), Coregonus. 



Subgroup b. The third and fourth vessels unite before 

 opening into the aorta, the common stem being 

 transverse to the length of the body. — Mur/il (fig. 8), 

 Hippoglossus (fig. 9), Pleuronectes, Osmerus (fig. 10), 

 Albula (fig. 11). 



Subgl'oup c. The third and fourth vessels unite, the 

 common stem sloping backwards towards the aorta. — 

 Malapterurus (fig. 12), Scopelus, Ci/prinus (fig. 13), 

 Cobitis (fig. 14), Esox (fig. 15), Marcusenius, Anguilla 

 (fig. 16). 



Group C. The first and second efferent branchial vessels open into 

 the eirculus cephalicus, and the third and fourth into the 

 aorta immediately behind the eirculus. 



Subgroup a. The third and fourth vessels open into the 

 aorta together. — Labrax (fig. 17), Liocassis (fig. 18), 

 Callichthys (fig. 19), Clarias (fig. 20). 

 Subgroup b. The third and fourth vessels unite before 

 opening into the aorta, the common stem being trans- 

 verse to the length of the body. — Perca (fig. 21), 



