Stenhouse. — On the Anatomy of the Pig-fish. 115 



pterygoid, and quadrate are nearly horizontal. The pterygo- 

 palatine region is imperfectly ossified, and there is no separate 

 mesopterygoid. On the upper angle of the quadrate is perched 

 a small ossification — " pterygo-palatine " — which is carried so 

 far forward as to lose the typical articulation with the 

 parethmoid. The hyomandibular is a stout plate, with a pos- 

 terior process bearing the opercular. The premaxilla consists 

 of a short alveolar plate, and a long semi-cylindrical nasal 

 process bound immovably to its fellow of the opposite side. 

 The maxilla does not enter into the gape : it has two mesial 

 processes connected with their fellows of the opposite side 

 respectively above and below the combined nasal processes 

 of the premaxilla} ; and the bone rotates around the lower 

 process. In the lower jaw, the dentary forms a short V, with 

 its broad apex (anterior) joined to its fellow of the opposite 

 side by fibrous tissue ; hence the posterior extremities of the 

 rami can be approximated. The articular bears a saddle- 

 shaped facet for the quadrate, and its anterior part projects as 

 a lamina into a cavity in the dentary. Meckel's cartilage 

 can be traced forward on the inner surface of the articular as 

 far as this cavity. The articular bears on its base and inner 

 surface a nodular angular connected by a strong ligament with 

 the interopercular. 



When the mouth opens, the dorsal angle of the dentary is 

 rotated forward, carrying with it the premaxilla, whose nasal 

 process, with its fellow, slides in the naso-prenasal groove. 

 These processes are connected by soft tissue with the walls of 

 the olfactory sacs ; and by their movements produce an ebb 

 and flow of the contents of the sacs. 



3. The Operculum. — The pre- and inter-operculars are 

 prolonged forwards like the suspensoria, and almost reach the 

 articular head of the quadrate. The preopercular alone has 

 a roughened skin-surface. The fan-shaped opercular is very 

 mobile on the process of the hyomandibular, and it and the 

 preopercular respectively hide the larger parts of the weak 

 subopercular and the bladelike interopercular. The pre- 

 opercular covers the posterior border of the hyomandibular, 

 but not the symplectic ; and receives the border of the quad- 

 rate into a groove on its upper border. 



4. Hyoid Ammratus. — The short cornua are suspended by 

 small interhyals from cartilage between the symplectic and 

 the hyomandibular. All the ossifications are small; and the 

 epi- and cerato-hyals bear equally between them the five thin 

 branchiostegal rays. The couple of hypohyals are separated 

 from those of the other side by two small bony nodules and by 

 the head of the spatular urohyal. 



5. Branchial Apparatus. — The very short branchial arches 

 together form a very compact mass perforated by the pharynx, 



