828 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [82] 



This author then proceeds to give an interesting account of the de- 

 velopment of these aijpendages, and in the matter of structure says 

 they " consist mainly of fibers running longitudinally. I have not yet 

 examined them under the microscope." The doctor is under the im- 

 pression he has detected homologous structures in Lepidosteus, but as 

 to their function he remarks that " I am not aware that any use has 

 been assigned to these appendages, and I have no suggestion to offer. 

 The anterior is evidently passive. The posterior, even if voluntarily 

 movable by the fish, is too flexible for offense, and is, moreover, covered 

 by the operculum," and with regard to morphological significance " un- 

 less some function can be assigned to these appendages the conclusion 

 that must naturally suggests itself is that they are remnants of organs 

 which had greater size and performed some function in more or less 

 remote ancestors of Amia. The position and general appearance of the 

 posterior pair are not wholly contradictory of the idea that they may 

 have been accessory branchiae ; but this could hardly be surmised re- 

 specting the anterior pair, or the supposed homologous parts of Lepidos- 

 teus. The appendages should be examined in fossil Amia and Lepidos- 

 teus, and in other extinct Ganoids ; likewise should careful search for 

 them be made in all living Ganoids, and in the Teleostean genera Ulops 

 and Megalops, which possess some points of resemblance to Amia.^^ 



The opportunity has never been offered me to examine either of these 

 latter forms with the view of searching for these structures, and at the 

 present writing I am aware of no one who has thrown any further 

 light upon this subject since Dr. Wilder made the above observations. 



OF THE PELVIC BONES AND VENTRAL, FINS OF AMIA. 



In speaking in a general way of these structures, Professor Huxley 

 remarks, that " In all Elasmobranchs and Ganoids, and in a large 

 proportion of the Teleosteans, the pelvic fins are situated far back on 

 the under side of the body, and are said to be "ventral" in position ; 

 but, in other Teleosteans, the ventral fins may work forward, so as to 

 be placed immediately behind, or even in front of the pectoral fins. In 

 the former case they are said to be "thoracic," in the latter "jugular." 

 (Anat. Yert. Animals, p. 39.) These pelvic bones in our subject are 

 quite well ossified, and hold a typical " ventral " position. (Plate X., Fig. 

 26.) They are in two distinct pieces, each piece being shaped like a 

 paddle, with the blade directed forwards. In life they lie side by side 

 just beneath the skin, with the expanded blades in the horizontal plane. 

 Their anterior extremities are cut square across, while posteriorly they 

 are enlarged so these aspects present an elliptical face in each case. 

 In a specimen of Amia with a vertebral column 30 centimeters long, I 

 find the pelvic boues each to measure 2^ centimeters in length. So far 

 as this description goes it agrees very well with these parts, as they are 

 figured and described by Franque, but I find other structures here that 

 apparently are not referred to, in either way, by this anatomist. Now, 

 we discover behind each pelvic bone in Amia and articulating with the 



