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on tlie outer surface of the exoccipital marks the position of the dorso-lateral portion of this labyrinth 

 Space, and forms a continuation of the ridge on the pterotic that marks the course of the external 

 semicircular canal in that bone. 



The dorsal edge of the exoccipital reaches the ventral surface of the overhanging roof of the 

 skull and is there separated by a relatively wide band of cartilage from the ventral edge of the 

 pterotic, that edge of the latter bone here being presented naesially. This band of cartilage forms a 

 nearly longitudinal line along the bottom (roof) of the subtemporal fossa, and lies against the ventral 

 surfaces of the parietal and lateral extrascapular. 



On the hind edge of the lateral plate of the exoccipital there are two flat stout processes sepa- 

 rated by a deep and rounded incisure. The dorso-lateral process suturates with the pedicle of the 

 suprascapular, the ventro-mesial one suturating with, instead of articulating with, a process on the 

 anterior edge of the first vertebra. Antero-internal to the incisure between the bases of the two 

 processes, a canal traverses the meduUary plate of the bone, transmitting the occipital nerve or nerves. 

 Ventrally the exoccipital suturates with the basioccipital, in the manner already explained. On 

 the lateral surface of the bone there is a small foramen which doubtless transmits the nervus 

 glossopharyngeus, and posterior to that foramen there is a large pit, in the bottom of which there 

 are two to four foramina which open into the cranial cavity and doubtless transmit the nervus 

 vagus alone; the actual relations of these nerves to the bone not being determined for the reasons 

 already given. 



The EPIOTIC is a small bone that seems at first sight to bear no resemblance whatever to 

 the pyramidal bone of the other fishes of the group. The dorsal surface of the bone is flat and sub-oval 

 in shape, and on the ventral surface of this thin dorsal plate there are two relatively tall and thin 

 flanges. One of these flanges is straight and extends from about the middle of the mesial edge of 

 bone, postero-laterally to its lateral edge, the ventral edge of the flange suturating with the posterior 

 plate of the exoccipital. The postero-mesial surface of this flange is exposed externally, and forms 

 a surface strictly comparable to the postero-mesial surface of the bone in the other fishes of the group. 

 The second flange lies anterior to the first one and is strongly curved, the hoUow of the curve directed 

 forward and both ends of the flange reaching the antero -lateral edge of the bone and there vanishing. 

 The Space enclosed within the curve of this flange is roughened and suturates with the dorso-mesial 

 surface of the lateral plate of the exoccipital, as already stated. This roughened surface of the 

 epiotic thus corresponds to the ventral edge of that surface of the bone in the other fishes that forms 

 part of the mesial wall of the temporal groove. The temporal-groove surface of the bone of Dactylo- 

 pterus is accordingly whoUy wanting, or at most is only represented in a part of the thin lateral edge 

 of the bone, this edge being covered laterally and ventrally by the band of cartilage already described 

 between the pterotic and exoccipital. 



Between the two flanges on the ventral surface of the epiotic there is a space which forms 

 the dorsal portion of that part of the labyrinth recess which, as just above explained, must lodge 

 the posterior semicircular canal and the posterior portion of the external canal. The dorso-postero- 

 lateral portion of this labyrinth space is bounded externally here ventrally by the band of cartilage 

 between the pterotic and exoccipital ; temporal and posterior surfaces of the epiotic not here uniting 

 to form an angle which encloses the summit of the posterior canal, as in the other fishes. The large 

 flat dorsal surface of the epiotic gives support to adjoining portions of the parietal, lateral extra- 

 scapular and mesial extrascapular, and its mesial edge is in sutural contact with the lateral edge 



