BY J. DOUGLAS OGILBY. 15^ 



MONOCENTRID^. 



Body ovate, strongly compressed. Head large, with conspicuous 

 muciferous cavities, the snout blunt and gibbous, projecting 

 somewhat beyond the mouth. Mouth wide with oblique cleft, 

 the lower jaw included, broad and truncated in front, with an 

 o\al, glandular, luminous disc behind the angle. Premaxillaries 

 protractile, uniting to form a deep symphysial cavity, at the 

 bottom of which is a similar disc, and constituting the entire 

 dentigerous portion of the upper jaw; maxillar}^ narrow, sigmoidal, 

 hidden in front and behind by the shields of the orbital ring, 

 provided with a large supplemental bone. Teeth minute, closely 

 set, tubercular, covering the jaws, palatines, pterygoids, and 

 branchial arches; present or absent on the vomer; tongue tooth- 

 less or with scattei'ed patches of teeth. Nasal openings large 

 and patent, separated from one another by a narrow naked 

 isthmus, which is curved forward across but is not connected 

 with the deeper curtain which partially divides the nostril from 

 the wide and deep preorbital cavity; both nostril and cavity are 

 separated from the eye by a membranous curtain, which is 

 partially protected along its outer margin l)y a small pyriform 

 dermal shield; the two preorbital cavities are separated above by 

 a wide bony bridge but are continuous within, so that there is an 

 unobstructed view through the snout; each is provided with a 

 luminous disc near its upper and outer edge. Eye large, situated 

 in the anterior half of the head. Bones of the head rugose but 

 not spiniferous, forming a network, the smooth membranous 

 interspaces profusely punctured by small open pores; suborbital 

 ring narrow, in part aborted; opercle with a strong curved keel 

 traversing its upper moiety, but without prominent spine. Gill- 

 openings wide; gill-membranes separate, free from the isthmus; 

 gills four; the membrane behind the fourth closed; eight branchi- 

 ostegals; pseud obranchise present ; gill-rakers short and stout, 

 densely spinulose. Two separate dorsal fins, the first composed 

 of a few strong, rough, more or less isolated spines, which are 

 alternatel}' inclined to left and right; soft dorsal with ele^•en or 



