OCR Text |
Show 1899.] BLOOD-VESSELS OF TELEOSTEAN FISHES. 951 common trunk formed by the union of the third and fourth branchial vessels is shorter. In Centronotus and Trachinus the anterior prolongation of the circulus is wanting, but otherwise the vessels of the pharyngeal roof are disposed as in Anar-rhichas. The circulus of Sphyrcena is twice as long as broad, and the posterior angle is very acute ; the subclavian arteries arise farther forward than in Anarrhichas, and have more the relations of those of Labrus (fig. 24). Hemichromis differs from Labrus in having a much broader circulus cephalicus, and in the more posterior origin of the subclavian arteries. The circulus of Exocoetus (fig. 25) is oval and longer than broad; the coeliaco-mesenteric artery arises from the circulus cephalicus immediately to the right of the aorta. Owing to the absence of the fourth gill and its efferent vessel in Lophius (fig. 26), the right of this form to rank under subgroup C c rather than C a is somewhat conjectural. The matter is, however, of no great importance. The circulus is very wide, and the coeliaco-mesenteric artery, which is considerably thicker than the aorta, branches soon after its origin. Concerning Lophius Meckel has written (14. p. 192): " Lophius piscatorius hat, statt der gewohnlichen drei bis vier, nur zwei sehr lange Kiemenblutadern. Von der vordersten Kieme entsteht ein einfacher Stamm, der zweite wird durch die Vereinigung der zweiten und dritten Kie-menblutader gebildet, die ungefahr eben so lang als der gemein-schaftliche Stamm getrennt verlaufen." M y own observations are thus not in accord with those of Meckel. Most ichthyologists admit, with Muller (17. p. 47), that the three gills present in Lophius are the anterior three of the four gills more normally present; and the coupling of the first and second efferent branchial vessels, the third remaining solitary, is by analogy with allied forms a far more intelligible arrangement than that described in tbe above-quoted passage from Meckel's text-book. In Gottus (fig. 27), although the circulus is so wide in front, the anterior carotids lie very close together, and the transverse commissure, which takes a curious bend forward, is therefore short. The coeliaco-mesenteric artery of Trigla (fig. 28) is a double vessel arising from the common trunk of the last two branchial vessels of the right side. There are no differences between the efferent branchial systems of Trigla cuculus and T. gurnardus. The anterior part of the circulus cephalicus of Cyclopterus (fig. 29) is very curiously shaped, and the transverse vessel may possibly be wanting. I have been unable to find it in the three specimens dissected. In the figure of Cyclopterus given by Stannius (23. pl. v. fig. 1) the subclavian arteries are drawn too wide; and they are incorrectly described on page 156 as branchial veins. Lepadogaster does not differ materially from Cyclopterus, except that the anterior part of the circulus cephalicus conforms more to the normal type. Gobius differs from Gottus (fig. 27) in the wider separation of the anterior carotids, the greater breadth of the circulus cephalicus, the more posterior entry of the second |