EEPORT ON THE DEEP-SEA FISHES. 235 



The quadrate (q) is similar in shape to the metapterygoid, the handle of the fan being 

 formed by the condyle for the articulation of the mandible ; it is intercalated between 

 and forms broad sutures with the pterygoid bones. 



Very remarkable is the prgeoperculum {p7-), which is reduced to a short small bone 

 situated at the lower side of the quadrate bone. The ectopterygoid (ecp) is a long and 

 slender bone, thin and lamelliform in its posterior half, and subtrihedral anteriorly, the 

 trihedral portion being cartilaginous. Viewed from the inside of the mouth the greater 

 part of its surface is covered with minute toothlets and asperities, but the surface of the 

 trihedral portion is smooth, giving attachment to a small membranous lamella which 

 is covered with teeth and represents a rudimentary palatine bone (pal). The ectoptery- 

 goid is articulated to a condyle-like process of the ethmoid cartilage (fig. 3, cq/). 



The hyoid arch does not show any noteworthy peculiarity. 



The intermaxillary (fig. 1, im) occupies an obliquely transverse position at the lower 

 side of the rostrum ; its lateral terminal third is in juxtaposition with the maxillary, its 

 inner portion is somewhat dilated, and not provided with ascending processes ; 

 consequently it is fixed and not capable of any sliding downward or forward motion. 

 The maxillary [m) is rather short, sword-shaped, constricted behind its articulatory end, 

 and proximally terminating in a styliform curved process which leans against the 

 ethmoid cartilage behind the ethmoid process (em' or e of figs. 4 and 6); its dental margin 

 is slightly thickened, and its posterior margin crescent-shaped; it bears a lanceolate 

 single supramaxillary behind. 



The mandible (fig. 2) is a very thin bone, rather broad, longitudinally concave 

 below, and slightly convex on the side. No separate angular can be observed, but the 

 articular is curved upwards as a small hook behind the joint. The tooth-bearing portion 

 of the dentary is separated from the upper margin of the articular by a long and wide 

 slit which is closed by a fibrous membrane. Meckel's cartilage is very thin and 

 slender. 



The dermal and membrane bones on the side of the head (fig. 1) are semimem- 

 branous. The operculum (o) is thin, subtriangular, with radiating folds ; it is note- 

 worthy that the cartilaginous substance of its articulatory facet extends a little way in 

 the dii-ection of the folds. The suboperculum (so) is much ddated, twice the size of the 

 operculum, striated, with a frayed margin. The interoperculum (io) is small, and 

 consists of an anterior dilated and posterior styliform portion. The chain of infraorbitals 

 is quite straight, and extends from the tip of the snout to the hind margin of the sub- 

 operculum. They are almost membranous, and being reverted along the upper edge, 

 form the framework of a wide muciferous canal. The anterior which surround the rostrale 

 are very irregular in shape, and much reduced in size, whilst the hindmost, which overlies 

 the suboperculum, is merely a skinny lobe lacerated behind. 



Externally the segmentation of the vertebral column would appear to be complete ; 



