494 PEOF. EAY LAKKESTEE ON THE HEAETS OP 



transverse series. Their tunics are continued in four narrow raised stripes behind their 

 bases. So far I have found the arrangement of this part of the heart nearly identical 

 in two examples. On examining the first example a pair of small papillary promi- 

 nences were found in a line between the series of stripes and the spiral valve, imme- 

 diately in front of the latter. These stripes and papillae appeared to me to represent 

 rudiments of a second and third series of valves, analogous to the plurality of series in 

 other ganoid fishes. Remembering, at the same time, the fact that individual variations 

 in the development and number of valves are not of uncommon occurrence in these 

 fishes, I examined the heart of a second (smallei', female) specimen, and had the satis- 

 faction of finding my supposition confirmed. In this specimen there are, in the series 

 corresponding to the pair of small papillee, four valves corresponding in position to, but 

 much smaller than, the permanent large valves which I have described above." 



Further on the same distinguished zoologist observes, in speaking of the relationship 

 o{ Lepidosiren and Ceratodus to one another and to the Amphibians (p. 552) : — "The 

 singular arrangement of the valves in the conus arteriosus is a point of much deeper 

 interest [than the difierences in the lungs and ovaries respectively]. There cannot be 

 a question that Ceratodus should be referred to Miiller's subclass of Ganoids, and ex- 

 cluded from that of Dipnoi, according to the chief characteristics by which he has 

 defined these divisions." 



Finally, in giving these genera their systematic position. Dr. Gunther places them in 

 a suborder " Dipnoi " of the order Ganoidei, and each in a distinct subfamily of the 

 family " Sirenidse." The subfamily " Ceratodontina," with the single genus Ceratodus, 

 is defined by the following characters : — " Conus arteriosus with transverse series of 

 valves. Ovaries transversely lamellated. One continuous vertical fin." The subfamily 

 " Protopterina," with the two genera Lepidosiren and Protopterus, is thus defined : — 

 " Conus arteriosus with two longitudinal valves. Ovaries closed sacs. One continuous 

 vertical fin." 



The quotations above given from Dr. Giinther's admirable monograph are sufficient 

 to show the importance attached to the valvular structures in the arterial cone of these 

 fish-like organisms. The fact that Dr. Giinther had noticed considerable variation in 

 the number and form of the valves in the specimens examined by him led me to make 

 a careful examination of these parts, and of the heart generally, in one of two fine 

 specimens of Ceratodus recently purchased for the Museum of Comparative Anatomy 

 in University College, London. I am glad to be able to gratefully acknowledge, on 

 the present occasion, the liberal manner in which the Council of that Institution have 

 seconded my efforts to form a typical collection of zoological specimens for the poj'- 

 poses of class-instruction. 



The heart had been removed from one specimen of Ceratodus, at my request, by 

 Mr. Ewart, the Curator of the anatomical collections ; and, accordingly, I shall not 

 now have any remarks to oifer on the course and mode of entrance of the large veins 



