226 Dr. A. Giintlier on Ceratodus. 



glandular mass. Not only the liver, but also the paired lobed 

 kidneys are provided with a portal system. The two ureters 

 enter by a single opening into a small urinal cloaca, situated 

 at, and partly confluent with, the dorsal wall of the rectum. 

 Vent in the median line of the abdomen ; a pair of wide peri- 

 toneal slits behind the vent. Testicle without developed vas 

 deferens, but with a duct running along its interior, blind at 

 both ends and without apparent outlet, but receiving the 

 semen from the canaliculi seminiferi. Ovaries transversely 

 laminate ; the ova fall into the abdominal cavity, and are 

 expelled by the peritoneal slits. A pair of narrow convoluted 

 oviducts are present, each being confluent with the ureter of 

 its side. It would appear, from the situation of the peritoneal 

 openings of the oviducts in the foremost part of the abdominal 

 cavity, and from the fact of one having been found closed, that 

 these ducts have no function. However, it must be remem- 

 bered that the female fish examined did not appear to have 

 attained to maturity. 



The evidence in favour of the close relationship between 

 Ceratodus and Leindosiren is so strong, that the difference in 

 the arrangement of the valves of the bulbus arteriosus can no 

 longer be considered to be of sufficient importance to distin- 

 guish the Dipnoi as a subclass from the Ganoidei. The 

 Dipnoi form a suborder of Ganoid fishes which may be cha- 

 racterized thus: — Oanoid fishes xoitli the nostrils within the 

 Tnoiith, with paddles siqiported by an axial sheleton, loith 

 lungs and gills and notochordal slceleton^ and icithout hranchio- 

 stegals. The Ganoids have hitherto been placed between 

 the subclasses Teleostei and Chondropterygii ; but they 

 are evidently much more nearly allied to the latter than to 

 the former, which, moreover, were developed in much more 

 recent epochs. Therefore I propose to unite the Ganoids 

 and the Chondropterygians into one subclass, Pal^ichthyes, 

 characterized thus : — Heart xoith a contractile hulhus arteriosus; 

 intestine xoith a spiral valve; optic nerves non-decussating . 



By a comparative study of extinct fishes, I have arrived at 

 some conclusions the substance of which may be shortly indi- 

 cated thus : — 



1. The suborder Dipnoi was represented in the Devonian 

 and Carboniferous epoclis by the genus Dijitertis (= Ctenodus), 

 in which I have also found the internal nostrils and a pair of 

 vomerine teeth j however, this genus is the type of a separate 

 family, on account of its heterocercy. 



2. The evidence with regard to Phaneropleuron (Huxl.) is 

 less conclusive; and Tristichoj^terus (Egert.), with the com- 

 plete segmentation of its vertebral cohunn, should be excluded 

 from this suborder. 



