1904.] OSTEOLOGY OF THE ELOPID^ AND ALBULID.E. 49 



remarkable that tlie pro-otic rises so high ;vs to touch tlie 

 frontaL 



The front part of the side of the basioccipital and the lower 

 part of the pro-otic are greatlj^ inflated, much as in Osmerus. 

 Incision into the bulla shows that it is for the accommodation 

 of the very large sacculus, with otolith of equivalent size, and not 

 for any diver ticiilum of the swim-bladder. The opisthotic is 

 moderately small, and lies equally upon the exoccipital, epiotic, and 

 squamosal ; it sends no process forward to meet the pro-otic. 

 The orbital surface of the alisphenoid is in a plane nearly 

 transverse to the axis of the cranium. The basisphenoid has the 

 form of a Y when seen from the front, but a thin plate of bone 

 continues forward from the stem of the Y into the interorbital 

 septum to meet the orbitosphenoid. The upper limb of the Y is 

 attached on each side to the alisphenoid and pro-otic. The 

 orbitosphenoid is largely developed, and, with the assistance of 

 the basisphenoid, forms a complete osseous interorbital septum. 



The pai-asphenoid extends very nearly to the occipital articu- 

 lation, and the eye-muscle canal opens posteriorly by a small 

 aperture. The part of the parasphenoid lying below the orbital 

 region bears numerous hemispherical teeth, disposed in a cofiin- 

 shaped patch. Just where the front of the parasphenoid meets 

 the back of the vomer is an oval space, which is roofed in by a 

 forward continuation of the dorsal part of the parasphenoid. The 

 vomer bears two or three transverse rows of pointed teeth. The 

 ethmoid region of the cranium is long, the distance from the front 

 of the mesethmoid to the back of the prefrontal being greater 

 than the length of the orbit. The mesethmoid projects consider- 

 ably in front of the vomer ; it has a trough on its upper surface 

 instead of the more usual ridge, and below the trough has a 

 foramen of elliptical shape, visible in a side view only. 



Temjjoral and Preopercular Serins. — The post-temporal has 

 three limbs. The largest lies over the epiotic, the second or deep 

 one is more slender, and is attached by ligament to the back of 

 the opisthotic, while the third one runs forward beneath the 

 supratemporal and spreads out into osseous tendons, to which are 

 attached fibres of the trapezius muscle, inserted into the posterior 

 temporal vacuity. The supratemporal has a rather flat external 

 surface, which is flush with the external surface of the squamosal. 

 The transverse commissure of the sensory-canal system, after 

 leaving the upper end of the supratemporal does not run in the 

 parietal, but superficially to its posterior edge. The preopercular 

 is bent at an angle of about 108 degrees, and the upper limb is 

 slightly longer than the horizontal limb. 



Circumorbital Series. — There are in all twelve bones of this 

 series (text-fig. 16, p. 50). The most anterior ones are curious, 

 basket-like bones, not much wider than the sensory canals which 

 they carry. The canals in this region are particularly large. 



Maxillary Series. — The upper part of the premaxill^ is sciilptured 

 into a spongy-looking basket-work similar to that of the naso- 

 lachrymal bones. Unless the mouth is very widely opened, the 

 Proc. Zool. Soc— 1904, Vol. II. Ko. IV. 4 



