218 



On (he Osteology of the Order Opisthomi, 



that tliese fishes are related to, but more specialized tlian, tlie 

 Percomorphi, but they show no particular aflfinitj to any 

 group of Percomorphous fishes. 



The skull is elongate, narrowed forwards, without crests or 

 ridges on the upper surface ; the parietals are separated by 

 the supraoccipital ; there is no opisthotic, but the other otic 

 boues are normally developed ; alisphenoids are present, but 



eoc 



SOC-' 



epo 

 epo^ 



.,'SOC / 



/ 



let/? 7? 



efh 

 r? elh 



'eoc psp pro v^i 

 p^o psp asp v pal 7? 



V 



-spo Uth 



Mastacembdus armatus. Skull from above, from the side, and 

 from below. 



p, parietal ; /, frontal ; «, nasal ; eth, mesetlimoid ; leth, lateral ethmoid ; 

 Vf vomer; pal, palatine; soc, supraoccipital; eoc, exoccipital ; boc, 

 basioccipital ; epo, epiotic ; pto, pterotic ; spo, sphenotic ; pro, 

 proctic ; asp, alispheuoid; psp, piu'aspheuoid. 



there is no basisphenoid nor orbitosphenoid. The nasals are 

 very large, meet in the middle line, and are firmly united to 

 the upper edge of the mesetlimoid, which forms a vertical 

 septum between the nasal cavities ; the prrvorbital is rather 

 large, articulates with the lateral ethmoid, and is attached to 

 the lower edge of the nasal ; the suborbitals are unossified. 

 The hyo-palatine and opercular bones are all present, but 



