DR. A. GUNTHER'S DESCRIPTION OF CEEATODUS. 
515 
trunk. The eye is small, lateral, much nearer to the extremity of the snout than to 
the gill-opening; orbit with a free edge. The mouth narrow, its corner being at some 
distance in front of the eyes ; lips rather thick and soft, simple, except on the side of 
the mandible, where the skin forms a simple, pendent fold. 
At the angle of the mouth, and hidden below a duplicature of the skin, there is an 
opening wide enough to admit an ordinary quill (Plate XXX. tig. 2, a ) ; it leads into a 
spacious cavity (b), irregular in shape, clothed with a mucous membrane, and containing 
coagulated mucus in which an immense number of mucous corpuscles are deposited. 
This cavity is separated from the cavity of the mouth by the membrana mucosa only, 
and there is no direct communication between them ; a branch cavity runs forward into 
the interior of the upper lip. 
The gill-opening begins on the side of the occipital region, and descends to below the 
pectoral paddle ; its entrance is covered, not by the bony gill-cover, but by a broad cuta- 
neous fringe of the operculum, the scales of this part of the cutis being very small. 
The foremost portion of the trunk is depressed, like the head, but it soon passes into 
the compressed remaining portion — the boundary between trunk and tail being exter- 
nally indicated by the vent only, which is in the median line of the abdomen. The tail 
evidently varies in length ; it is sometimes shortened, as I have also observed in Heterotis 
and other diphycercal fishes; and it appears that injuries of this part, particularly when 
inflicted in early youth, are readily repaired. The depth of the trunk decreases slightly 
behind ; and the tail diminishes rapidly in vertical dimension, till it ends in a thin point 
which is externally scarcely distinguishable, being enveloped by the vertical fin. 
The dorsal part of this fin commences as a low membrane on the back behind the 
middle of the trunk, and the anal part at a short distance behind the vent. It is sup- 
ported or formed by innumerable simple rays, becomes gradually deeper in the same 
proportion as the depth of the fleshy portion of the tail decreases, and finally tapers 
rapidly into a point. 
The limbs consist of two pairs of paddles, similar in appearance to the termination of 
the tail ; viz. a longitudinal axis, formed by the endoskeleton and muscles and covered 
with scales, is surrounded by a broad rayed fringe. These paddles are structurally iden- 
tical with the fins of Lejndosiren ; only the axis and also the fringe are much dilated. 
The pectoral and ventral paddles taper to a fine point, the former being longer than the 
head, the latter rather shorter. The ventral paddles are inserted at a short distance in 
front of the vent. 
The entire body is covered with very large scales , presenting on the exposed portion 
a smooth surface with several faint concentric lines of growth ; the margin is smooth 
and membranaceous. Towards the extremity of the tail the scales rapidly diminish, 
in size, passing into the small scales with which a great part of the vertical fin is covered. 
The axial portion of the paddles is also covered with small scales ; whilst the gill-cover 
is protected by small scales nearest to the branchial cleft, some large scales overlapping 
the small ones. The lateral line is clearly marked, its scales being perforated at the 
