168 DR. RICHARDSON'S DESCRIPTION OF AUSTRALIAN FISH. 



There are ten broad chisel-shaped teeth, more or less acuminated, belonging to the 

 upper jaw, and six with crescentic cutting edges, and one of the angles a little stronger, 

 implanted in the lower jaw. The posterior tooth on each side of the upper jaw has a 

 thin rounded edge, and appears at the angle of the mouth, overlapping the outer teeth 

 of the under jaw. The central pair of teeth both above and below converge at their 

 points. 



Osteology. — The intermaxillaries, closely applied in an even line to each other, are 

 convex above, dilated inferiorly, and joined by ginglyraus to the broad end of the 

 ethmoid by the interposition of a thin articular cartilage. The teeth are implanted 

 into them by sockets. The maxillary appears to have no motion : its upper end 

 is closely fitted to a triangular lateral process of the ethmoid ' , and its lower half to the 

 upper and outer edge of the intermaxillary. No suborbitars could be detected. The 

 preoperculum is much developed, a strong inferior limb running forwards with a shght 

 inclination upwards to the articulation of the lower jaw, and the upper limb running 

 backwards at a very obtuse angle with the former to the lower margin of the orbit. 

 The lower edge is thin and broad, and much rounded at the angle. The operculum and 

 suboperculura are elliptical ; the latter is the broadest of the two, and forms the greater 

 part of the anterior border of the gill-opening : it is not so wide as the border of the 

 preoperculum. The under branchiostegous ray is broad, more compressed and more 

 curved than the others, which are slender. 



Supra-scapular consolidated with the cranium, so as not to be distinguishable. Sca- 

 pular oval, articulated to the cranium, and lying wholly on the exterior side of the 

 coracoid which runs up behind it to join the cranium. The third piece of the humeral 

 chain, named 'humerus' by Cuvier, but 'coracoid bone' in the last edition of the 

 ' Anatomic Comparee,' is very large, and forms the whole posterior edge of the gill- 

 opening. Its interior plate is very broad, meeting its fellow of the opposite at the 

 mesial isthmus, and resting firmly against it. The radius (Cuv.) is also developed into 

 a broad plate with a strong elevated edge, and is applied along the under side of the 

 coracoid up to the isthmus, serving to enlarge the fossa for the reception of the muscles 

 which move the fin. The ulna on the other hand is small, being in proportion to the 

 moderate-sized pectoral fin. The styloid bone, strong, long, flat, and linear, is articu- 

 lated at its upper end to the interior surface of the elbow, which the coracoid forms 

 over the pectoral fin. The pelvic bone is long and consists of an upper keel, and a 

 less extensive under one united by a thin vertical plate. The bone emerges anteriorly 



' In Tetraodon, this angular process, instead of lying further back than the end of the ethmoid, projects 

 beyond it, and the maxillary is articulated to it, not by its e.\treme upper end, but by a shoulder. The 

 maxillary itself is united by bone for a considerable part of its length to the intermaxillary, but its rounded 

 end projects beyond that line at the angle of the mouth. The dilated lower end of the intermaxillary of Mo- 

 nacanthus rudis resembles the maxillary of Tetraodon in form ; but if it is to be considered as actually represent- 

 ing that bone, it will differ in being still more intimately consolidated with the intermaxillary, and also in 

 furnishing a socket for the last tooth of the upper jaw. 



