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Show 1899.] BLOOD-VESSELS OF TELEOSTEAN FISHES. 945 with very similar vascular arrangement, but with widely different epipharyngeal dentition, may be mentioned the Salmon and tbe Mackerel. In the Salmon there are a pair of small patches of teeth borne by the fourth epibranchial bones, lying immediately ventral to the aortic extremities of the third efferent branchial vessels; but in the Mackerel there are a pair of great den-tigerous pads underlying the mesial ends of the second, third, and fourth efferent branchial vessels, as well as a considerable part of the circulus cephalicus. In the Carp the dorsal aorta obtains the necessary protection by actually traversing the great horn-covered bony projection of the basioccipital, against which the lower pharyngeal teeth bite. In the Wrasse the vascular arrangement conforms to a very average type, being apparently quite unaffected by the large aud elaborate pharyngeal mill developed in the vicinity of the posterior half of the circulus cephalicus. In Exocoetus, again, the epipharyngeal pad is of relatively enormous size, underlying the upper extremities of all four efferent branchial vessels, the anterior ends of the aorta and cceliaco-mesenteric artery, and the whole of the circulus cephalicus except the extreme anterior part ; yet there is nothing very remarkable in the disposition of these vessels which might be accounted for by their relation to the epipharyngeal apparatus. Only in Gobius, Cottus, and Molva, of the forms examined, are the epipharyngeal dental pads situated entirely within the circulus cephalicus. The evidence afforded by forms devoid of epipharyngeal teeth is probably inconclusive, on account of the great possibility of the edentulous condition having been arrived at independently in different groups of fishes, in the Sprat and Pipe-fish the types of vascular arrangement are widely divergent. The Sprat closely resembles the Herring (fig. 2 ) ; the vessels of Syngnathus are shown in figure 33. In order to discuss intelligibly the different forms of vascular arrangement met with, some form of classification, however artificial, is essential; and after careful consideration I have found it convenient to adopt the following scheme, based on the relations of the efferent branchial vessels to the circulus cephalicus and the dorsal aorta. In consideration of the unsatisfactory nature of the present classification of Teleostean fishes, a purely artificial scheme, founded upou the single character which forms the basis of the present communication, is likely to prove of more permanent utility for purposes of subsequent reference, than one which relies upon a classification which sooner or later may prove to be an unnatural grouping. The great majority of the forms studied will be seen to come under the headings B and C, while the rarer and more extreme modifications occupy terminal positions in the classificatory scheme. The division of the groups B and C into the subgroups b and c differing only in the transverse or oblique position of the confluent third and fourth efferent branch'a vessels, appears arbitrary, but in practice there are very few torms which fai to |