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Show 1899.] BLOOD-VESSELS OF TELEOSTEAN FISHES. 947 Mullus, Corvina, Equula, Zeus (fig. 22), Trachinus, Anarrhichas (fig. 23), Zoarces, Gentronotus, Sphyrcena, Labrus (fig. 24), Hemichromis, Exoccetus (fig. 25). Subgroup c. The third and fourth vessels unite, the common stem sloping backwards towards the aorta.- Lophius (fig. 26), Coitus (ng. 27), Trigla (fig. 28), Cyclopterus (fig. 29), Gobius, Fistularia (fig. 30), Lepado-gaster, Saccobranchus (fig. 31), Silurus (fig. 32). Group D. The four efferent branchial vessels open into the circulus cephalicus. Subgroup a. The third and fourth vessels open separately. -Syngnathus (fig. 33), Motella. Subgroup b. The third and fourth vessels open together.- Gastrosteus, Gadus (fig. 34), Molva, Hippocampus. Subgroup c. The third and fourth vessels unite before joining the circulus cephalicus.-Blennius (fig. 35), Orthagoriscus (fig. 36), Tetrodon (fig. 37). SPECIAL PART. In the case of species not figured, comparisons will be drawn with those figured forms which, in the arrangement of the efferent branchial vessels, they most nearly resemble, irrespective of the degree of affinity which upon other grounds may be considered to exist between the forms. FURTHER REMARKS ON GROUP A. In Engraulis (fig. 1), there is a considerable difference in the size of tbe four efferent branchial vessels; the second is the broadest, and the first the narrowest. The dorsal aorta behind the fourth branchial vessel is wide and very thin-walled. This is also the case in Clupea. Although the scheme of classification which it has been found convenient to adopt brings Ammodgtes (tig. 3) under the same subgroup as Clupea (fig. 2), there are several features which go to show that the association is an unnatural one. The circulus cephalicus in the former genus is much longer than broad, and extends back nearly to the point of entry of the second pair of vessels into the aorta; whereas in Clupea the posterior part of the circulus is transverse to the axis of the body, and forms with the first part of the aorta a T rather than a Y. The cceliaco-mesenteric artery arises in Ammodgtes close behind the fourth efferent vessels, but} much further back in Clupea. The origin of the subclavian arteries is slightly more posterior in Clupea than in Ammodgtes. There are no differences between Ammodgtes lanceolatus and A. tobianus, nor between Clupea harengus and G. sprattus. Chirocentrus closely resembles Megalops (fig. 4). In both genera the median aortic stem found in Engraulis and Clupea |
