ICHTHYOLOGY. 



223 



Introduc- 

 tion- 

 Digestive 

 Sj'stem. 



their 



with the bone is less complete, 



above the general surface. 



In Diodon, we have the same 



kind of single tooth in each 

 jaw, or rather confluence of 



teeth and jaw. In Telrodon, 



the dentiferous jaws are 



divided by a mesial suture 



so as to present two com- 

 pound teeth above and as 

 many below. 



In the Plagiostom.es, the 

 teeth are limited to the maxil' 

 lary and mandibular bones, 

 while in the genus Ci/prinus J 

 teeth are wanting in the jaws, 

 but, as mentioned above, 

 these fish have grinding teeth jaws 

 on the pharyngeals and basi- 

 occipital. In the Cataslomi 

 of the Cyprinoid family, the 

 pharyngeal teeth are arranged 

 on a crescentic bone like the 

 teeth of a curved comb, the 

 points being thickened for 

 grinding. In Scarus, besides the solidly aggregated jaw- 



rise as such. 



The Lampreys have rows of teeth on the lips, as Introduc- 

 tion. 



of 



Fig. 65, 

 Hoplegnatltus (Searodon 

 Schlegel), Tbe upper jaw is consti- 

 tuted by the pre-maxillaries coaleB- 

 cent into a single bone, and having 

 the teeth so intimately incorporated 

 with their substance as to make a 

 solid, smooth, gorget-shaped bone; 

 the forms of the teeth, however, 

 faintly showing. The same is the 

 case with the maxillary, the syraphy- 

 sial line being obliterated as com- 

 pletely as in the human under jaw. 



Fig. 5G, 



Teeth of Calliodon chlorolepis^a Scaroid fish from Hong Kong. In this genus 

 the teeth are less intimately united to the jaw-bones than in Scarus and 

 SopUgnathus. In the upper jaw the teeth consist of narrow chisel-shaped 

 denticles, so grouped as to indicate four teeth with curved crenaled edges 

 on each pre maxillary and limb of the dentary piece of the maxillary. In 

 tbe latter the four teeth stand out more distinctly, the one next the 

 medial line being so intimately coalescent with its fellow as to form merely 

 one tooth of the same shape as the others, and seated in front of the sym- 

 physis. So considered, it is a pairless median tooth, followed on each side 

 towards the corner of the mouth by three others. There are also two small 

 subulate canines or buck-teeth on each pre-maxillary. Tlie fish is the 

 "Scaly King-tisher" of the Cliinese, who give it this name because it has 

 bright celandine-green, orange, and yellow colours. 



teeth above mentioned, there are also pharyngeal grinders. 



In Crenidens, thin tricuspid teeth placed 



in many close rows on the jaws, serve to 



cut the tender fuci on which these fishes , 



feed. In passing through the whole series ' 



of fishes, we find teeth on the nasal bone, 



as in Murana, where they stand in a row 



round the edge of the bone, and in one 



down the longitudinal mesial line ; on the 



pre-maxillary, the maxillary, the palatines. Fig. 67, 



the vomer, the hvoid-bones, the branchial '''""i "[ Tetrodon 



arches, and especially on their processes, Ostracioniriw fam 



named " rakers." Teeth occur on the 



maxillary only when it enters into the 



composition of the orifice of the mouth, as 



in the Clupeidm and Salmonidce. In 



Pristis, of the Ray tribe, the flat snout, 



greatly prolonged, and well ossified, is set 



on each side by a series of very strong nail-shaped teeth, 



whence its name of Saw-fish among sailors, though it is 



in reality a wea])on that wounds by repeated blows, not 



by cutting longitudinally like a saw. This snout forms a 



dangerous sword in the hands of the Polynesians who use it 



ily of Fiectognaths, 

 similar to those of 

 Scants and Hoplcg- 

 nathtts, but the me- 

 sial symphysis of 

 both jaws remain- 

 ing non-coalescent, 

 four teeth are 

 formed, as thegene- 

 ric name denotes. 



Fig. 58. 



Jaws of Enchetynasm Bleekerl, one of the Murtenldo!. In this genus, teeth 

 stand round the edge of the nasal bone and down its mesial line : two small 

 ones exist on the vomer ; two rows on the palatine bones and mandible. 

 The liinder nostril is funnel -shaped. 



Fig, 59. 



Jaws of Braehysomophis horridits, one of the OphisuridcBy which have one row 

 of teeth round the margin of the nasal, one row down the mesial line of 

 that bone, and one on the vomer ; a row on the mandible, and two rows 

 on the palatines. 



Fig. GO. 

 Jaws of Plectropoma denUx. 



well as strong pharyngeals. Commonly the teeth do not 

 cross the symphysis of the jaw, there being in most cases 

 a line of division between the pre-maxillaries or at the union 

 of the limbs of the mandible. Instances to the contrary 

 have already been mentioned in Scarus, Hoplegiiathus, and 

 Diodon. In Notidamis, Sci/mnus, and Myliobates, among 

 the Plagiostomi, we have also examples of this departure 

 from the dental type of the higher animals. 



