— 126 — 



there is, in Trigla, a sliglit projecting ledge, this being niuch more marked in mv small specimens 

 than in the large one used for the drawings. The hind edge of this ledge, in the small specimens, 

 projects posteriorly as a sharp angle, and beneath this part of the ledge the dorsal surface of the 

 condylar process of the exoccipital gives support to the lateral portion of the base of the first vertebral 

 arch. The mesial and larger portion of the base of the arch rests upon a portion of the dorsal surface 

 of the articular process of the independent centrum of the first vertebra, this surface of contact lying 

 postero-mesial to and contiguous with the sixpporting surface on the exoccipital. The arch does not 

 come into contact with the basioccipital. 



The mesial process of the exoccipital, so well developed in Scorpaena, is but slightly developed 

 in Trigla. It is directed ventro-mesially, at about 45 ", its ventral end, which is widely separated 

 from its fellow of the opposite side, resting upon a small process-like portion of the dorsal surface 

 of the basioccipital, this part of the basioccipital forming the mesial wall of the hind end of the 

 saccular groove. 



The BASIOCCIPITAL is broad and relatively short. Its anterior end is deeply and widely 

 excavated by the hind end of the myodome, a narrow, longitudinal, and slit-like opening leading 

 from this groove onto the outer surface of the bone. That part of the basioccipital that forms the roof 

 of the myodome is flat and inclines downward and backward almost at an angle of 45", thewide and 

 relatively shallow saccular groove of either side being, in consec[uence, pushed on to what appears 

 as a lateral portion of the cerebral surface of the bone, and being also tilted upward at a considerable 

 angle. The hind end of the saccular groove forms a recess in the basioccipital, and between the 

 recesses of opposite sides there is, on the dorsal surface of the bone, a large median pit which is the 

 cavum sinus imparis. Posterior to this pit, and at a considerably higher level, a short portion of the 

 dorsal surface of the bone forms the floor of the foramen magnum. The hind end of the bone is irregulär, 

 the appearance being that of the ordinary vertebra-like hind end of this bone, with the dorso-lateral 

 Corners deeply cut away. This leaves a depressed surface on either side of the dorsal portion of the 

 hind end of the bone, and this depression receives and gives support to the anterior articular process 

 of the first vertebra. On the lateral surface of the hind end of the bone there is a flattened surface 

 which gives origin to the occipito-supraclavicular ligament. 



The centrum of the FIRST FREE VERTEBRA is an irregulär disk of bone without attached 

 dorsal arch. The posterior surface of the disk has the usual concave vertebral depression, while on 

 its anterior surface there is simply a flat or slightly concave median portion. From the dorso-lateral 

 portion of the centrum, on either side, a stout process projects antero-laterally, rests upon the basi- 

 occipital in the depressed region at the dorso-lateral corner of its hind end, and there articulates 

 with the condylar process of the exoccipital. The bases of these two anterior articular processes of 

 the first centrum are joined by a stout web of bone which forms a shelf projecting forward from the 

 dorsal edge of the centrum, thus making the dorsal surface of the centrum much wider, antero- 

 posteriorly, than its ventral surface. On either side of the dorsal surface of the centrum there is a 

 depression which receives the ventral surface of an anterior process of the second vertebra, this latter 

 process bearing and being fused with the base of the preforaminal portion of the arch of its vertebra. 

 This process of the second vertebra, in small specimens, but not in the large one used for the 

 figures, extends, in its lateral portion, almost to the anterior end of the corresjjonding process of the 

 first vertebra, the free arch of this latter vertebra thus appearing, in lateral views, to rest almost 



