Miscellaneous. 351 
type of this order among the Ganoids; and Dr. Giinther, going 
still further, regards the Dipnoi as nothing more than a suborder of 
the Ganoids, and thinks that these latter should be united with the 
Plagiostomi, to form with them a single order (Paleichthyes) charac- 
terized by a heart furnished with a contractile arterial bulb, an 
intestine with a spiral valve, and uncrossed optic nerves. 
The discovery of Ceratodus Forstert certainly seems to diminish 
the value of the order Dipnoi. This fish, which approaches Lepido- 
siren in regard to its respiratory apparatus, departs from it, on the 
other hand, by the structure of its heart, which is perfectly 
ganoidean, consisting only of two cavities with an arterial bulb ; 
moreover the intestine is furnished with a spiral valve. The genus 
Dinichthys is a new type, which, combining the osteological charac- 
ters of the Lepidosirens and those of the Placoderms (cuirassed 
Ganoids), furnishes an additional argument in favour of M. Gervais’s 
opinion and establishes a fresh transition between the different 
groups of Ganoids. 
Besides its great size (a cranium measures 3 feet in length and 
2 in breadth) the Dinichthys is especially remarkable by its denti- 
tion. The lower jaw consists of massive rami, the posterior extre- 
mities of which are rounded and flat. The anterior part of each 
ramus is bent upwards so as to form a sort of strong, acute, and 
prominent tooth ; behind this tooth the jaw is thickened by a bony 
projection on the inside, which terminates in front in a triangular 
process like a tooth ; beyond this process the margin of the mandi- 
ble is compressed for a distance of 5 or 6 inches, and consists of a 
very dense bone-like enamel; in one species this margin is entire 
but trenchant; in another it is denticulated with conical points 
half an inch long. 
The upper jaw consists of two triangular premaxillaries, constitu- 
ting, as it were, two great incisors, followed by two maxillaries 
with trenchant or denticulate margins. This structure much 
reminds us of the dentition of Lepidosiren and Coccosteus ; and the 
resemblance becomes still more striking when we compare figures 
representing these three forms. Unfortunately, the upper part of 
the cranium being but imperfectly known, we cannot tell whether 
the bones called premaxillaries by Mr. Newberry are or are not 
the homologues of the dentigerous nasals of Lepidosiren ; but with 
respect to the mandible the resemblance is as complete as could be 
desired. 
The body of Dinichthys was covered with a buckler composed of 
plates exactly similar to those of Coccosteus decipiens, of the same 
number, and arranged in an almost identical manner, the only 
differences shown by a comparison of the figures being a certain 
narrowness of the buckler and the termination in a sort of point of 
the outer angle of the posterior plates. 
The jaws of Dinichthys present several points of resemblance to 
those of Coccosteus ; but this is not the case with the cranium and 
the back, the bony armour of which, in the former fish, much more 
resembles that of Asterolepis and Heterosteus. Whilst the outer 
