134 ELOPIFORM FISHES 



to be fused with the articular. The Meckelian cartilage rests on a ledge on the medial 

 face of the mandible. The sesamoid articular is partially embedded within the 

 cartilage. 



Circumorbital series. The circumorbital series is composed of six infraorbitals, 

 three rostral ossicles, an antorbital and a supraorbital. 



The orbital margin of the six infraorbitals is rolled laterally so forming a ventrally 

 incomplete tube round the sensory canal. The first infraorbital is large with a 

 rounded anterior margin. Much of the maxilla is covered by this element. Pos- 

 teriorly the first infraorbital partially overlies the second of the series but the 

 connection between these bones is flimsy and they separate easily. As is usual in 

 elopiforms the third infraorbital is the largest of the series. This element is angled 

 and the posterior margin exhibits a shallow indentation. The fourth and fifth 

 infraorbitals form a narrow inclined strut . The sixth infraorbital, or dermosphenotic, 

 has no direct contact with any other bone but lies free in the skin. In all, the 

 posterior infraorbitals are quite distinct from those of Albula, as may be seen by 

 comparing Text-figs. 66 and 80. 



The antorbital is a narrow, elongate ossification which together with a similarly 

 shaped supraorbital forms a flexible strut serving to help expand and contract the 

 supraorbital nasal diverticulum. The importance of this strut in relation to the 

 functioning of the diverticulum has been noted by Derschied (1924) and Gosline 

 (1961). The three small rostral ossicles lie free from one another and from any 

 neighbouring bone. The margins of each ossicle are rolled over to contain the sensory 

 canal. 



Opercular series. The shape of the operculum, suboperculum, preoperculum and 

 interoperculum may be seen in Text-figs. 65 and 66. The suboperculum is notable 

 in having a particularly long dorsally directed anterior wing which almost reaches 

 to the level of the opercular process of the hyomandibular. The interoperculum, 

 which resembles a branchiostegal ray, is joined anteriorly to the rear of the mandible 

 and posteriorly to the suboperculum by ligaments. The preopercular sensory canal 

 runs within a short bony tube dorsally and is protected ventrally by a large flange of 

 bone. The middle portion of this canal lies free in the skin. 



Cephalic sensory canal system. The sensory canals of the head are more open than 

 in any other albuloid. For the most part the canals lie within troughs covered by 

 taut skin. 



The supraorbital canal passes through the frontal for a very short distance, much 

 of its length being accommodated within the frontal trough. Anteriorly the supra- 

 orbital canal continues within the gutter-like nasal and ends blindly at the tip of 

 the dermethmoid. The supraorbital canal connects with its partner of the opposite 

 side through a large fenestra in the dermethmoid ridge. In two of three specimens 

 examined in this respect a single neuromast was observed in the skin at the base of 

 this fenestra (a feature previously noted by Gosline 1961) and this neuromast, like 

 others of the supraorbital canal, is supplied by the superficial ophthalmic nerve. In 

 the third specimen examined no neuromast could be seen. 



The otic sensory canal lies within a groove upon the pterotic. Anteriorly the otic 

 canal joins the supraorbital and infraorbital canals in the skin immediately above the 



