NO. 3 TELEOSTEAN FISHES — GOSLINE 2$ 



snout region is a series of six small ossicles on each side, several of 

 these bearing a single neuromast. 



The supraorbital and antorbital in relation to olfaction. — For 

 present purposes the nasal organs of the lower teleosts may be di- 

 vided into three types. One, represented in the fishes examined only 

 by the Beloni formes, has no nostrils and no olfactory laminae, at 

 least in Cololahis and Hyporhamphus ; instead, the nasal tract runs 

 directly to the base of a nasal tentacle which protrudes from a nasal 

 fossa. Variations of this nasal organ in the hemiramphids have 

 been described by Weed (1933, p. 44). A second type of nasal 

 structure consists of a series of transverse laminae lying at the 

 bottom of a nasal capsule that is closed above except for two rather 

 small, well-separated nostrils. The anterior of these frequently opens 

 at the tip of a tube. Water is presumably passed across the nasal 

 epithelium of such an olfactory organ by ciliary action as in Anguilla 

 (Liermann, 1933). In fishes with either of the types of nasal organs 

 just noted the surrounding bones appear to have little to do with ol- 

 faction, and these types will not be dealt with further. 



In the majority of living teleosts, by constrast, there are two rela- 

 tively large, adjacent narial openings leading into the olfactory cap- 

 sule on the bottom of which lie the olfactory laminae. From the 

 capsule extend one or more nasal sacs or diverticula. Movement of 

 the bones around these sacs alternately contract and expand them, thus 

 pumping water in and out across the nasal epithelium (Eaton, 1956). 

 It is with certain of the bones involved in this pumping system that 

 the present discussion will be concerned. 



The antorbital (fig. 7B, AN) is a bone rather widely represented 

 among the lower teleosts but apparently incorporated into the lacrimal 

 in higher forms. It undoubtedly originated as a sensory canal bone, 

 but in living lower teleosts it serves primarily as part of the nasal 

 pumping system just mentioned. 



For purposes of nomenclature, the "type" antorbital is that of Amia 

 (Westoll, 1937, p. 519)- However, it seems probable that the antor- 

 bital of Amia is equivalent to the two lateral rostrals plus the antor- 

 bital of Elops (cf. Westoll, 1937, p. 519, footnote). In modern 

 teleosts the antorbital becomes associated with the supraorbital bone 

 (fig. 7B) above it and reduces or loses its sensory canal. Even so it 

 remains easily identified by its topographic position and relationships : 

 when present it lies above the lacrimal and borders the nasal openings 

 below ; forward it usually has a ligamentous connection with the outer 

 surface of the maxillary. Only when the antorbital is greatly reduced 



