524 Reviews— Fritsch’s Paleozoic Dipnoi. 
this genus may eventually prove to be so arranged as to appear the 
homologues of the dental cusps of Ctenodus tuberculatus has also 
still to be substantiated by future discoveries. 
Ctenodus is defined as ‘a Dipnoan of Ceratodus-like structure. 
Dental plates with many notched ridges. Dermal bones of the 
head more numerous than in Ceratodus. The hyoid and the entire 
skull more elongated than in Ceratodus. The skeleton more com- 
pletely ossified than in Ceratodus, but otherwise agreeing with the 
latter in detail. Scales large, thin, of elongated quadrangular form, 
bearing traces of fine rows of denticles; with vascular grooves on 
the under side.” All the portions of the skeleton are then described 
under the heading of Ctenodus obliquus, Hancock and Atthey, it 
being quite impossible to separate the bones of a second species (OC. 
applanatus, Fritsch) that also occurs at Kounovaé. The more im- 
portant fossils were obtained from the pyritous shales in the latter 
locality ; and it is disappointing to read that Dr. Fritsch’s admirable 
galvanoplast reproductions of the Stegocephalians met with so few 
purchasers, that it has been deemed impracticable to secure perma- 
nent copies of these new destructible Ichthyolites by the same costly 
process. 
In the skull of Ctenodus there are several ossifications in parts 
that remain permanently cartilaginous in Ceratodus; and many 
interesting comparisons are made. A bone that was formerly 
described as the pelvis of a Stegocephalian, is now recognized as 
the squamosal of Ctenodus. The cranial roof bones appear to defy 
all attempts at definite nomenclature; and there is no distinct 
evidence of ossified maxillee and premaxilles, The opercular bones, 
with the exception of the operculum itself, are also not yet capable 
of certain determination. With regard to the mandible, Dr. Fritsch 
identifies a small fossil with the thin plate described by Huxley 
in Ceratodus as the dentary element; and a figure is given to illus- 
trate the insignificant dimensions of this bone, and the importance of 
its claims to recognition as a peculiar ‘dermomental” element. 
The small development of the dentary bone, however, in certain 
Mesozoic Ganoids with crushing teeth (e.g. Pycnodonts and Belono- 
stomus), seems to render the original as ee inaenes quite as plausible 
as that now suggested by Dr. Fritsch. 
The teeth referred to C. obliquus in the present monograph were 
at first made known by Dr. Fritsch under the name of Ceratodus 
Barrandei; and an interesting series is figured to show the changes 
that appear to take place in the dentition during the growth of the 
fish. The Professor remarks :—‘“ We possess a series of the teeth, 
from 11 to 54 mm. in length, and there is really no doubt that these 
belong to different stages in the life-history of a single species. They 
are two and a half times as long as broad, and the number of notched 
ribs varies from 7 to 9. The most anterior seven ribs are especially 
prominent, but the eighth and ninth are at times indistinct, and then 
follow two or three small tubercles, which represent additional 
crimped ribs. The ribs decrease in length backwards, so that the 
seventh is only half as long as the first. The crimping is mostly 
