This genus agrees with SCIAPHOS, PYXICEPHALUS, and PELOLATES, in having a large, sharp-edged tubercle on the inner edge of the ankle, but it differs from them at first sight, by the head and body being compressed and high, the mouth very large, and the eyes convex on the side of the forehead.

PERIALIA EYREI, t. 2. f. 3.—­Olive, sides of the face, and body blackish brown; face varies with white streak; the sides of body marbled with unequal white spots; limbs brown and white marbled; under side of the body whitish.

Inhab.  Australia, on the banks of the river Murray.

PERIALIA?  ORNATA, t. 2. f. 2.—­Pale grey, back and sides, marbled with symmetrical dark-edged spots, those of the middle of the back being generally confluent, of the face elongate, band-like; the legs dark-banded, beneath white.

Inhab.  Port Essington.

Somewhat like DISCOGLOSUS PICTUS in appearance.  The internal nostrils are far apart, with an elongate group of palatine teeth level with their hinder edges.

Taking advantage of the space of the plate, figures of the following species from the same country, which have not hitherto been illustrated have been added.  They were described or noticed in the list before referred to.

1.  Cystignathus dorsalis, t. 1. f. 2.  Gray, Ann.  Nat.  Hist. 1841.

2.  Phryniscus Australis, t. 2. f. 1.  DUM.  And bib.  E. Gen. viii. 725.  Bombinator Australis, Gray, proc.  Zool.  Soc. 1838. 57.

III.  Mr. Eyre having brought home with him the drawing of a species of cray-fish found near the river Murray, which is called by the natives UKODKO, I have been induced to examine the different species of Astaci in the British Museum collection, which have been received at various times from Australia, for the purpose of attempting to identify it.

As we have three very distinct species which have not yet been described or figured in any of the works which have passed under my inspection, I shall proceed to detail their peculiar characters and give figures of their more characteristic features.

The drawing of “the UKODKO or smaller Murray cray-fish” most nearly resembles ASTACUS Quinque-CARINATUS, but it is three or four times larger than any of the specimens of that species which we possess, and the figure does not shew any indications of the five keels on the front of the head.  In wanting the keel on the thorax it agrees with an Australian species described by Mr. Milne Edwards under the name of ASTACUS AUSTRALASIENSIS, said to come from New Holland, and to be about two inches long, while Mr. Eyre’s figure is more than six inches, and is said not to be taken from a large specimen.  It differs from Mr. Milne Edwards’ figures, in having only one spine on the wrist, so that probably there are still two more species of the genus to be found in Australia.