] 899.] BLOOD-TESSELS OE TELEOSTEAN FISHES. 945 



with very similar vascular arrangement, but with widely different 

 epipharyngeal dentition, may be mentioned ' the Salmon and the 

 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 Mackeiel 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 aoi'ta 

 obtains the necessary protection by actually traversing the great 

 horn-covered bony projection of the basioecipital, against M'hich 

 the lower pharyngeal teeth bite. In the Wrasse the vascular 

 arrangement conforms to a very average type, being apparently 

 quite unaffected by the large and elaborate phaiyugeal mill 

 developed in the vicinity of the posterior half of the circulus 

 cephalicus. In Exoccetus, again, the epipharyngeal pad is of 

 relatively enormous size, underlying the upper extremities of all 

 four efferent branchial vessels, the antei-ior ends of the aorta and 

 coeliaco-mesenteric arteiy, and the whole of the circulus cephalicus 

 except the extreme anterior part ; yet there is nothing verv 

 remarkable in the disposition of these vessels which might be 

 accounted for by their relation to the epipharyngeal apparatus. 

 Only in Gohius, Cothcs, and Molva, of the forms examined, are the 

 epipharyngeal dental pads situated entirely within the circulus 

 cephalicus. The evidence afforded by forms devoid of epi- 

 pharyngeal 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 

 Syngnaih'us are shown in tigure 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 ha\'e 

 found it convenient to adopt the following scheme, based on the 

 relations of the efferent branchial \ essels to the circulus cephalicus 

 and the dorsal aorta. In consideration of the unsatisfactorv 

 nature of the present classification of Teleostean fishes, a purely 

 artificial scheme, founded upon 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 pi'ove 

 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 classiticatory 

 scheme. The division of the groups B and C into the subgroups 

 b and c, differing only in the transverse or obliqne position of tlie 

 confluent third and fourth efferent branch'a a essels, appears 

 arbitrary, but in practice there are very few torms which fai to 



