THE MORMTEID^, NOTOPTElilDvT;, AND HTODONTIDJi;. 195 



at first appears to be one long continuous head, although 

 strictly the anterior extremity, immediately over the foramen, is 

 a small separate head. The axis of the hyomandibular is inclined 

 in a forward direction, and, in the absence of a distinct 

 symplectic, is attached to the postero-superior edge of the 

 quadrate. 



Opercular Series (figs. 5 and 9). — The subopercular is small, 

 and is concealed in a lateral view by the lower part of the 

 opercular bone. The branchiostegal rays are eight in number 

 on each side, and, with tbe exception of the last but one, all are 

 slender and of uniform width. The first four are attached to 

 the outer face of the ceratohyal, the next two to the epihyal, 

 while the last two are free from the epihyal, but lie close under 

 the ventral edge of the opercular bone. 



HyohrancMal Series. — The first, second, and third basi- 

 branchials are ossified, the first being the largest and the third 

 the smallest. There is no giossohyal. There is a dentigerous 

 membrane-bone, nearly circular in outline, overlying the middle 

 part of the first basibranchial, and immediately behind it is 

 another dentigerous membrane-bone, longer and narrower than 

 the former, and covering the hinder part of the first basibranchial 

 and the anterior half of the second. The teeth upon these 

 bones have single^oints like those of the parasphenoid. The third 

 basibranchial has the form of a rod curved into the fourth part 

 of a circle, so that, while its anterior part is horizontal, its 

 posterior part projects down vertically between the downwardly 

 directed third hypobranchials. The relations of the hypo- 

 branchials and the pair o£ tendon-bones are exactly as in 

 Mormyrops. 



The urohyal is short, and consists mainly of a vertical sheet 

 o£ bone less than twice as long as high ; it articulates with the 

 ventro-internal surfaces of the anterior ends of the ceratohyals, 

 and also by au extensive articular surface with the under parts 

 of the posterior three-fourths of the first basibranchial and the 

 anterior one-fourth of the second basibranchial. 



The ceratohyals are short and wide. There is but a single 

 hypohyal to each, the upper of the two normally present in 

 Teleosteans. It is small in size, and is wedged closely beneath 

 the anterior o£ the two dentigerous bones. 



There is no first pharyngobranchial, nor a spicular bone ; the 

 second pharyngobranchial is a horizontally disposed plate of 



14* 



