Stenhouse. — On the Anatomy of the Fig-fish. 113 



B. Skeleton. 



1. Cranmm. The cranial cavity is wide and slightly de- 

 pressed, although the entire head is compressed. The cranial 

 bones are mainly well developed, no distinction being seen 

 in the adult between cartilage and membrane bones. The 

 main cartilage is a median prenasal and nasal mass con- 

 tinued backwards as the interorbital septum. In the entire 

 specimen the size of the cranium is exaggerated by two 

 large parietal plates continuing the side- walls upward. The 

 cranium adheres closely to the form of a regular box whose 

 posterior almost vertical end has the atlas firmly attached 

 to it by both the condyle and the circumference of the 

 vertical ovoid foramen magnum. The latter is bounded 

 below and laterally by the exoccipitals, and above by the 

 epiotics. The basioccipital enters into the formation of 

 the cranial floor, where it lodges the auditory vestibules 

 in a pair of depressions ; and it forms the lower third of 

 the condyle, the remainder of which belongs to the ex- 

 occipitals. The cranial floor presents ventrally a well- 

 marked median ridge formed by the vomer and the long 

 parasphenoid which sheaths the basioccipital. The large 

 shield-shaped supra-occipital is shifted forward to the centre 

 of the cranial vault, and rests by two downwardly-directed 

 processes on the sphenotics, while its incompletely ossified 

 anterior border is continued forward beneath the frontals by 

 cartilage, which splits in front into two parts, which turn 

 downwards and backwards, to be continuous with the flat 

 orbito-sphenoids. The latter form the lateral parts of the 

 anterior cranial wall, which is inclined forward at an angle of 

 45°, and is incomplete mesially, where a sheet of soft tissue 

 receives the posterior border of the interorbital septum. 



The deviations from the typical form might be thus ex- 

 plained : The epiotics have met by strong processes above the 

 foramen magnum, and have displaced forward the large supra- 

 occipital ; the latter has displaced outwards the parietals 

 which form the upper part of the cranial side-walls and a 

 small part of the roof. The ' ' -otic ' ' bones are carried outward 

 and downward, and the sphenotic and pterotic (the latter 

 transmitting the horizontal semicircular canal) form the lower 

 part of the side- wall and the outer part of the floor. The 

 prootic is entirely in the floor, which also includes the hori- 

 zontal halves of the opisthotic and exoccipital ; the vertical 

 halves of these two latter enter into the cranial posterior wall, 

 the former external to the latter. 



Typical epiotic processes are represented by relatively small 



epiotic spines united with very large plates, which form the 



main parts of the parietals. Instead of a supra-occipital crest 



or spine, there is a faint groove, continued into a deeper groove 



8 



