THE CONUS ARTERIOSUS IN TARPON ATLANTICUS 

 (CUVIER & VALENCIENNES). 



H. D. SENIOR, M.B., F.R.C.S. - 

 ASSOCIATE IN ANATOMY, WISTAR INSTITUTE OF ANATOMY, PHILADELPHIA. 



The tubular prolongation of the arterial end of the heart 

 furnished with numerous valves, and known as the conus arteri- 

 osus, is one of the characteristic features of elasmobranchs and 

 ganoids. In Aniia calva, the conus arteriosus is relatively shorter 

 than in other ganoids, and its valves are reduced to three trans- 

 versely arranged tiers. It may be said that the absence of the 

 conus arteriosus as a separate structure is a characteristic of the 

 teleostean heart, and that this fact is emphasized by a few recorded 

 exceptions, all of which occur in teleostean families more or less 

 closely related to Anna. 



Among these exceptional teleosts only one has been hitherto 

 described, which possesses more than one tier of conus valves, 

 this is Butirimis (Albula) which has two, and to it may now be 

 added Tarpon atlanticns. 



The heart from which the following description is taken, was 

 sent to me by Mr. Charles H. Townsend, director of the New 

 York Aquarium. It comes from a specimen 5 feet 4 inches in 

 length. 1 I take this opportunity of thanking Mr. Townsend for 

 his courtesy in sending this heart, also an entire Tarpon, 4 feet 

 4 inches long, the heart of which is shown in Fig. 3. 



The conus of Tarpon atlanticus resembles that of Aniia calva 

 in form, but differs from it in being proportionately smaller, in 

 having two tiers of valves instead of three, and in appearing to 

 have been driven into the heart towards the apex, so that, 

 instead of projecting freely from the ventricle, as in Aniia, it is 

 more or less buried in the latter. 



In the natural position, the conus of Tarpon is a horizontally 

 placed longitudinal tube, elliptical in transverse section. The 

 longest diameter of the ellipse is dorso- ventral, and measures 16 



1 Measurements include caudal fin. 



146 



