200 DE. W. G. EIDEWOOD ON THE CEANIAL OSTEOLOGY OF 



(3) XX. 1853, p. 160), and Boulenger (Poissons du Bassin du 

 -CoBgo, 1901, p. 50, footnote) all record the number as four. 



The epihyal is relatively longer and larger than in other Mormy- 

 roids : there are no hypobyals. The urohyal is fused with that 

 bone which in Mormyrops (p. 191) was taken to represent the 

 first basibranchial and the endosteal glossohyal combined. This 

 compound bone is the No. 33 of Erdl (bottom of plate, left-hand 

 side) ; its front part is marked a, and its hinder part h in Hyrtl's 

 figure 2 of plate 1. The great pair of tendon-bones {g of Hyrtl's 

 figure) show less evidence of containing a hypobranchial element 

 than in other Mormyroids; they are strongly curved, and extend 

 horizontally outward and then backward. Their antero-internal 

 •extremities are closely bound by ligament in the median plane, but 

 partially between them, and projecting a little in front of them, 

 is a small rod of bone, the reduced second basibranchial. In 

 Hyrtl's figure the letter h, although not on the bone, but to the 

 right side of it, is evidently intended to apply to it, for he 

 describes h as " der mediane Knochenkern in der Symphyse der 

 mit g bezeichnete Knochen." There is no third basibranchial. 



Touching one another above the glossohyal is a pair of small 

 bones, apparently representing the dentigerous membrane-bone, 

 although they are toothless. They are not shown in Hyrtl's 

 figure, but one of them is shown in Erdl's lower figures ; it 

 is marked No. 35, and is called (p. 228) " kleines Zungen- 

 beinhorn, ein langlicher, ziemlich cylindrischer Knochen. Beide 

 kleine Horner stossen mit ihrem vorderen Theile an einander, 

 nach hinten divergiren sie." In a footnote on the succeeding 

 page, Erdl compares these small bones with the unpaired 

 dentigerous membrane-bone that lies over the endosteal glosso- 

 hyal of Mormyrus. 



The first hypobranchial * is a small rod-like bone, lying across 

 the anterior extremity of the first ceratobranchial ; it fails by a 

 good deal to reach the median line. The second hypobranchial 

 may be fused with the paired tendon-bone, but the third hypo- 

 branchial is wanting. The reduction of the hypobranchials, 

 however, does not bring the anterior ends of the cerato- 

 branchials closer to the median line. The ceratobranchials 

 of the right and left sides remain, in fact, widely separated. 



The four epibranchials are short and subequal. There is no 



* This and the pharyngobranchials are not shown in Hyrtl's figure. 



