26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I42 



is it difficult to identify. Nevertheless it passes under a number of 

 names in the literature. Thus Derschied (1924) calls it the adnasal; 

 Gregory (1933) labels the same bone prefrontal in some illustrations 

 (e.g., fig. 32) and lacrimal in others (e.g., fig. 40) ; and Wohlfahrt 

 (1937), Berg (1940), Kirkhoff (1958), and others have mistakenly 

 identified it as a supraorbital bone. On the other hand Lekander 

 (1949) has, with more justification, called the bone usually termed 

 the lacrimal, the antorbital. In the cyprinids which Lekander studied, 

 the bone in question is very probably a compound structure made up 

 of a fusion of the lacrimal and antorbital, but the latter bone would 

 seem to have formed at most a very insignificant part of the result. 



In living teleosts there is at most only one supraorbital bone (fig. 

 7B, SU). It never bears a sensory canal and seems to be the sole 

 remnant of a series of bones that formerly protected the upper border 

 of the orbit. In certain scopeliform fishes (e.g., Aulopus) the re- 

 maining supraorbital forms part of the rigid roof of the orbit, but its 

 retention in modern teleosts is probably attributable to its secondary 

 association with the antorbital as part of the nasal pumping system. 



In the majority of modern isospondylous fishes there are two nasal 

 sacs opening off from the nasal capsule (Derschied, 1924). The lower 

 of these passes down and back in front of and below the orbit. Water 

 is pumped in and out of this sac by movements of the lacrimal dorso- 

 lateral to it and the palatine ventromedial to it. (This is the Lacrimal- 

 sack of Liermann, 1933 ; see also Eaton, 1956.) The upper sac, with 

 which the present discussion is concerned, extends up and back to 

 and sometimes above the upper border of the eye. As Kirkhoff ( 1958) 

 has clearly shown for Clupea, the expansion and contraction of this 

 sac is governed by the linkage of the antorbital (supraorbital I of 

 Kirkhoff) and supraorbital. Movement in the superficial bones of the 

 snout associated with both nasal sacs is ultimately controlled by the 

 opening and closing of the mouth. This is brought about by separate 

 ligamentous attachments between the maxillary and the forward ends 

 of the lacrimal and the antorbital. 



Neither the presence of an upper (supraorbital) nasal diverticulum 

 nor of an antorbital-supraorbital link are constant features in the 

 isospondylous fishes (Derschied, 1924). It would seem that wherever 

 a well-developed supraorbital nasal sac is present there is also an 

 antorbital-supraorbital pumping mechanism. However, the supraor- 

 bital or antorbital bone may be present in fishes with no supraorbital 

 diverticulum. With this introduction, a brief history of the antorbital 

 and supraorbital bones in living teleosts will be given. 



