ESOCIN^. 



HEMIRAMPHUS. 



301 



among the mackerel. The sub-gemis Hemiramphus Cuv. 

 is another subordinate type of this genus ; and its sin- 

 gular mouth is perfectly unique among fishes : the lower 

 jaw is of the same proportionate length as in the gar- 

 fish, but the upper is so short that it appears as if 

 broken off almost at its base. It would be highly inter- 

 esting to know those particular habits which require a 

 structure of mouth so different from all other fishes ; 

 but this remains unknown. Various species are found in 

 the tropics of both hemispheres : one of these_, the Hem. 

 Brasiliensis ? (^fig. 64^.), we have examined in a fresh 



state^, and thus been able to detect a singular pecuHarity, 

 not yet noticed. On both sides of the lower jaw (which, 

 in its depressed shape^ resembles the upper one of a 

 saw-fish deprived of its spines) is a thin membranaceous 

 fringe or skin_, very delicate, and which is half the 

 breadth of the jaw itself: it is quite clear that this jaw 

 is not used either to secure the food upon which this 

 fish may feed, for the point of it is quite obtuse ; neither 

 can it be employed to thrust into the sand or other 

 substances, for then this membrane would be destroyed 

 immediately : besides, the circumstance of the other 

 gar-fish swimming close to the surface of the water, 

 shows that their food is not found at the bottom ; and 

 this also must be the case with Hemiramphus, whose 

 shape and general structure, in every thing but its mouth, 

 is perfectly the same as Ramphistoma. Now it is a re- 

 markable circumstance, that we have a genus of birds. 



