DR. RICHARDSON'S DESCRIPTION OF AUSTRALIAN FISH. 153 



having a different aspect from those of the body than by its bounding ridges. The 

 breadth of the head between the eyes equals the vertical diameter of the orbit. The 

 nostrils are situated in a soft membrane immediately before the eye, the posterior open- 

 ing being the largest, and having a curved, elliptical form, with the lining of its bottom 

 perforated by a series of openings arranged in a crescentic line. The anterior opening 

 has an oval shape, and is about half the size of the other ; it shows some membranous 

 folds within. The exterior edges of both openings are thin and not in the least elevated. 



The mouth opens beneath the head, considerably behind the apex of the snout. The 

 intermaxillaries forming the crescentic margin of the upper jaw are capable of protru- 

 sion in a vertical plane to the extent of the third of an inch : when retracted they slip 

 nearly under the scaly integument. The lower ends of the maxillaries are but just per- 

 ceptible in the loose integuments at the corner of the mouth, even in the most extended 

 state of the jaws. The lower jaw opens and shuts in a hinge-like manner into the upper 

 one, whether the latter be protruded or retracted. A small tapering barbel hangs from 

 behind its symphysis. 



Teeth. — The intermaxillaries and lower jaw are armed with villiform teeth, the 

 dental surface being broadest at the mesial line, and narrowing to a point on the limbs 

 of the bones. The teeth are small, slender, and acute, slightly curved backwards, and 

 so crowded that the rows cannot be counted on either jaw ; the dental surface is evi- 

 dently rather wider on the upper jaw. The tongue, palate, and vomer are toothless. 

 There are three upper pharyngeal bones on each side, two of the pairs armed with 

 larger teeth, and the anterior pair with much smaller ones. The lower pharyngeal 

 teeth form a triangular patch, divisible into two by a mesial line. All these teeth are 

 similar in structure, each consisting of a cylindrical cartilaginous stem, crowned by a 

 short conical point of enamel which wears down to a ring. The teeth on the jaws 

 exhibit the same form under a lens. The largest pharyngeal teeth are not above the 

 third of a line in diameter, and only about a line in length. 



Scales. — The branchiostegous membrane, the margins of the eye and nostrils, the 

 lips and part of the lower jaw are the only scaleless parts of the head, and there is 

 even a scaly patch on the posterior part of each limb of the lower jaw. The scales on 

 the body are moderately large and strong, and are all armed by longitudinal or slightly 

 radiating ridges, composed of closely incumbent tiled spines, the last one forming a 

 tooth-like projection on the edge of the scale. Tlie scales on the middle of the body are 

 largest, and are armed by about eighteen ridges ; they are smaller near the head and on 

 the tail, where they have only about twelve ridges. The scales on the opercular bones 

 are smaller than those on the body, and do not overlap each other ; and on the rest of 

 the head they are still smaller with much fewer ridges, but from the spines being less 

 evenly tiled, they are rougher. Even on the under surface of the head, where the scales 

 are so minute and uniform as to seem like the points of shagreen, each scale contains 

 one or two ridges of spines, which under the lens are seen to be still more divergent and 



