— 169 — 



edge of the epiotic. The hind end of the bone gives support, as already stated, to the anterior end 

 of the suprascnpular. 



The pterotie of Dactyh)pterus thus has no exposed surface corresponding to the one that 

 forms part of the lateral bounding wall of the temporal fossa in the other fishes of the group. That 

 portion of the temporal fossa that is usuaUy bounded by this bone is thus either wholly absent in 

 Dactylopterus, or it has been reduced, by the compressive action that has given rise to the subtemporal 

 fossa, to a narrow space that lies between the pterotic-exoccipital band of cartilage, just above referred 

 to, and the overlying dermal bones on the dorsal surface of the skull. The band of cartilage is evidently 

 the homologue of the cartilage that forms the bottom of the temporal fossa in the other fishes, and 

 as this cartilage is certainly not in synchondrosis with the overlying dermal bones, a thin space must 

 exist between them, in the place where the temporal fossa is usually found. A further possibility 

 regarding a portion of the fossa will be referred to when describing the suprascapular. 



The BASIOCCIPITAL is broad and thin, is slightly convex on its internal and slightly concave 

 on its external surface, and the median longitudinal line on its ventral surface presents a slight 

 reentrant angle. On the hind end of the bone there is a deep median pit which extends forward to 

 the line of the reentrant angle and represents the vertebral depression on the hind end of the bone. 

 Lateral to this pit, the wide flange-like portions of the bone give support, on their dorsal surfaces, 

 to the ventral edges of the exoccipitals. Anteriorly the bone suturates with the proötics and para- 

 sphenoid. A very slight depression on either side of the internal surface of the bone forms the hind 

 end of the saccular groove. Between these two depressions there is, in the anterior portion of the 

 bone, a slight median depression, the significance of which could not be determined in my limited 

 material. The anterior edge of the bone is grooved, and encloses the hind end of the thin median 

 sheet of cartilage that connects the ventral edges of the proötics of opposite sides. The median 

 portion of the hind edge of the dorsal surface of the bone forms the ventral boundary of the foramen 

 magnum. 



The EXOCCIPITAL has a concave lateral and a strongly reentrant posterior surface. The 

 latter surface has the two usual portions, one of which forms part of the hind wall of the cranial 

 cavity while the other arches over the meduUa, the two portions appearing, in the disarticulated bone 

 as a stout, tall, V-shaped ridge arising from the dorso-mesial surface of a sub-oval bone. That part 

 of the posterior portion of the bone that arches over the meduUa has a thick dorso-mesial edge, which 

 suturates in part with its fellow of the opposite side but mainly with the ventral edge of the spina 

 occipitalis. The dorsal edge of that part of the bone that forms part of the hind wall of the cranial 

 cavity suturates with the ventral edge of a strong ridge on the ventral surface of the epiotic, this 

 ridge forming the posterior surface of the latter bone. Slightly antero-lateral to this ridge on the 

 epiotic, a relatively large V-shaped portion of the ventral surface of that bone is in sutural contact 

 with a corresponding surface on the dorso-mesial surface of the lateral plate of the exoccipital; this 

 latter surface of contact extending downward from the dorsal edge of the exoccipital nearly to the 

 central point of the bone. Between the portions of these two bones that have these two sutural 

 connections — the lateral and posterior plates of the exoccipital, below, and the epiotic above — 

 there is a tall and narrow space which must lodge the posterior portion of the external semicircular 

 canal, the larger portion of the posterior canal, and possibly also the hind end of the utriculus; but 

 want of material prevented my determining the exact relations. A broad, low and rounded ridge 



Zoologica. Heft 67. 22 



