494 PROF. RAY LANKESTER ON THE HEARTS OF 
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 papille 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 yalves are not of uncommon occurrence in these 
fishes, I examined the heart of a second (smaller, 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 papille, 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 
of 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 differences 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. Giinther places them in 
a suborder “ Dipnoi” of the order Ganoidei, and each in a distinct subfamily of the 
family “Sirenide.” 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 puy- 
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 offer on the course and mode of entrance of the large veins 
