I 



and their Anatomical peculiarities. 327 



by long ribs, and, including the head and chest, is semicircular in form 

 in front ; and, while its general form is remarkably oblique, and more or 

 less elliptical, it is a little elongated backwards to the point where its 

 forked taU (which is about one-fourth of its length) begins. The hack 

 rises into a sharp ridge, wliich, at its middle, supports a single fin ; be- 

 hind this fin there is a small gibbosity or hump (membranous in the spe- 

 cies of Hermann, and Olfers, muscular in that horn Celebes), in a situation 

 corresponding to the adipose and rudimental fin of the Salmonidse, while, 

 in front of the dorsal fin, the carinated fore part of the back after be- 

 coming sulcated, ends in two sharp ridges, which converge towards the 

 upper part of the head, at the interparietal bone, and thence running 

 downwards, finally diverge towards the nares at the middle of the upper 

 lip.* The trunk presents inferiorly, between the extremities of the hu- 

 merals and the crests of the pelvic bones, a sharp pellucid ridge or crest, 

 a formation which depends upon the acute junction of the extremities of 

 the ribs. On each side of this carinated ridge there is a row of from 

 eight to twelve small depressed surfaces, corresponding, for the most 

 part, to the extremities of the intercostal spaces, but which, having been 

 regarded as folds of the textures around the sternum (a bone merely as- 

 sumed to exist), suggested the name of Sternoptix. The anus is mean 

 (i. e. equally placed between the head and tail). The caudal region \s 

 slightly convex, and terminates by an acute carinate edge, running along 

 one-third of the length of the body. The outline of the head is, ante- 

 riorly, remarkably obtuse, and the height of that region is double its 

 length. The eyes are large, salient, and naked ; they occupy the middle 

 third of the height of the head, and advance within a line of its anterior 

 boundary. The mouth, which is directed upwards suddenly, descends 

 very obliquelj', so as to appear abrupt when viewed in front, and is there- 

 fore singularly capacious in the vertical direction ; and the maxillary 

 bones (the upper of which slides over the lower) form the superficial 

 boundary of this opening. The tongue is small and rudimental. Maxil- 

 lary teeth exist in the Sternoptix : these are very numerous and minute. 

 They differ, however, in the several species, both in their form and ar- 

 rangement, appearing either en velours (as in the S. Hermanni) or en cro- 

 chets (as in the S. Olfersii and S. Celebes). 



The Branchiostegous Membrane is patent, though posteriorly its mar- 

 gin is retracted under the opercula, and in each of the semicircular inter- 

 spaces of the branchial rays it exhibits a longitudinal depression or shal- 

 low sinus. 



The Branchial Rays arc from five to nine in number, very slender, naked 

 at the extremity, and they curve downwards, backwards, and inwards. 



Opercules. The opcrcule is subarcuated, soft, fine, and elastic, and 

 terminates inferiorly in a right angle, the anterior margin of which is pa- 

 rallel to the last branchial ray, and partly covers it. The two branchial 



* See Plate III. fig 2. 



