ESPECIALLY MYCTOPHOIDS 125 
margin of the operculum is straight and slightly oblique. An inner strengthening 
ridge runs from the region of the facet anteriorly and traverses the medial face of 
the bone to terminate on the small posterior spine. The suboperculum is prominent 
and like the operculum bears an inner strengthening ridge. Both bones are orna- 
mented with tubercles, those on the operculum radiating outwards from the anterior 
edge of the bone in the region of the opercular facet. 
Pectoral and pelvic girdles and fins. The post-temporal has an oval upper limb whose 
dorsal surface is ornamented with tubercles. The supracleithrum could not be seen 
since it lies medial to the upper opercular region. The cleithrum is large and 
ventrally it is expanded both anteriorly and posteriorly. The anterior end of the 
cleithrum almost reaches the preoperculum, while the posterior end projects back- 
wards beyond the insertion of the pectoral fin. Ventrally the lower margin of the 
cleithrum is inflected towards the mid-line. The lateral face of the cleithrum bears 
the same tubercular ornamentation as the opercular bones and the tubercles are 
more pronounced ventrally. The pectoral fin arises just below the middle of the 
flank and appears to consist of approximately 12 rays forming a moderately large fin. 
The pelvic bones are prominent and each consists of a thin sheet of bone roughly 
triangular in shape. The pelvic bones lie immediately posterior to the cleithrum and 
thus can be said to be sub-thoracic in position. The pelvic fins are as large as the 
pectoral fins and are composed of 7 or 8 stout rays. 
Median fins and tail. The dorsal fin is situated behind the mid-point of the body 
and is composed of 14 rays. The first ray is small and unbranched, the second ray is 
the longest and the remaining rays decrease in length. All the rays are segmented, 
and except for the first are branched. The pterygiophore number parallels the 
number of fin rays, and the first 3 proximal radials are expanded, especially the 
first which bears an expanded anterior median keel. The anal fin is remote and 
consists of 15 or 16 rays ; unlike the dorsal fin, none of the proximal radials is 
expanded. 
The caudal fin consists of Ig principal rays. Accessory caudal rays are present in 
front of the principal rays both above and below the fin, there being between 18—20 in 
all. 
Vertebral column. The vertebral column has some 41 or 42 vertebrae of which 
approximately 22 are caudal. In the anterior precaudal region the first few centra 
are long and narrow and mesially constricted. The centra begin to shorten in length 
at about the roth precaudal vertebra and by the 14th precaudal vertebra they have 
become reduced to a length which remains constant to about the 13th caudal (the 
34th vertebra). From this vertebra to the end of the column the centra become 
further reduced in length and depth so that at the caudal peduncle the centra are very 
small and practically square. The neural arches are prominent and the line of 
articulation between the arch and the corresponding centrum is clearly visible. The 
neural spines are short and arise from the posterior region of each neural arch. In 
the precaudal region the neural spines are at their longest and exhibit a slight 
backward curvature. Below the dorsal fin the spines shorten and straighten, and 
