ESPECIALLY MYCTOPHOIDS 121 
within the bone ventral to the facet. The tube which contained the sensory canal 
passes forwards on the ventro-lateral region of the articular and opens into a shallow 
groove on the posterior region of the dentary. The lateral face of the mandible is 
ornamented with bony tubercles which run in regular lines radiating backwards from 
the symphysial region on the dentary, and forwards from the facet region on the 
articular. The ornamentation is more pronounced antero-ventrally where the 
tubercles are raised on bony ridges. 
The angular is a small knob of bone forming the postero-ventral angle of the mand- 
ible. 
Opercular bones. The opercular bones are shown in medial and lateral views in 
Text-figures 53, 54. The preoperculum is deep, narrow and forwardly inclined 
ventrally. Dorsally it ends behind the head of the hyomandibular where it rests 
against the posterior face of the crest on the hind edge of the hyomandibular. More 
ventrally the anterior edge of the preoperculum is excavated vertically, so that a 
slight concavity is produced into which the posterior edge of the quadrate fitted. 
Ventrally again the preoperculum is produced into a small backwardly projecting 
spine. The preopercular sensory canal ran within a tube in the bone opening dors- 
ally by a single pore, and ventrally by two or three pores. Two of the ventral pores 
open posteriorly on the region of the spine, whilst the most anterior pore opens 
anteriorly on to the articular. The lateral face of the preoperculum is ornamented 
with characteristic bony tubercles which are more prominent in the region above the 
sensory canal and along the posterior margin of the bone. Ventrally on the pre- 
opercular spine the tubercles are raised on ridges of bone. 
The operculum has a straight anterior edge covered by the preoperculum laterally. 
The dorsal border of the operculum is rounded but ventrally the edge is concave. 
From the articulatory facet midway along its anterior edge an internal horizontal 
strengthening ridge crosses the bone and terminates on the posterior angle where it is 
produced into a short spine. Laterally the operculum is ornamented with radiating 
rows of bony tubercles arising from the point of articulation with the hyomandibular. 
The suboperculum is large with its dorsal part lying medial to the ventral region of 
the operculum. The lateral face of the bone is ornamented with a regular arrange- 
ment of bony tubercles. 
Genus SAURORHAMPRHUS Heckel, 1850 
D1AGnosis (emended). Eurypholidae in which the head is elongated, especially in 
the preorbital region where it is extended into a prominent rostrum. Vertebral 
number 42 of which 22 are caudal. Body very shallow, never exceeding the depth of 
the head, and extended by an increase in the length of the individual centra especially 
precaudally. Pelvic fins and pectoral fins of equal size ; pelvic fin almost sub- 
thoracic in position. Mid-dorsal scutes 6 or 7 in number, overlapping each other 
in advance of the dorsal fin. 
TYPE SPECIES. Saurorhamphus freyeri Heckel. 
