ESPECIALLY MYCTOPHOIDS 193 
Both families have a reduced squamation, scales being present only along the 
lateral line and in the mid-dorsal line anterior to the dorsal fin. In the Enchodon- 
tidae this squamation is further reduced and neither the mid-dorsal scutes nor the 
lateral line scales overlap. The mid-dorsal scutes are most prominent in the 
undeepened species, e.g. Palaeolycus dreginensis (Text-fig. 43), and are smallest in 
those species of Enchodus which have some post-cranial deepening, e.g. Enchodus 
marchesetur (Text-fig. 41). In the Eurypholidae both series of scutes are well 
developed, especially those in the mid-dorsal line. In Eurypholis boissieri there is 
evidence that a sensory canal passed through the mid-dorsal scutes (p. 110). This 
median sensory canal presumably connected with the supratemporal commissure on 
the supraoccipital (Text-figs. 44 and 49). The lateral line scales are larger and more 
prominent in the Eurypholidae, but in both families the scales are of identical shape. 
Each scale bears a small pointed prominence. The prominence is smallest at the 
anterior end of the lateral line, but towards the caudal peduncle the spines become 
produced into larger hook-shaped projections. This increase in size is most marked 
in the Enchodontidae (Enchodus major) where the last lateral line scale bears a large, 
pointed horizontal flange projecting outwards and backwards. Monod (1959) 
noticed a similar latero-caudal spine in Acanthurus monroviae formed from a modified 
scale. Monod found no intrinsic musculature in the spine and it did not secrete 
venom, but he could give no suggestions as to its function. It can only be suggested 
that the spine in Enchodus may have had some stabilizing effect during swimming, or 
possibly an offensive effect if the tail was thrashed through the water. 
These familial differences can possibly be related to a basic divergence in habitat 
and mode of life. Both families are clearly composed of predatory species with 
streamlined bodies, stout jaws, and a formidable armament of teeth. The Enchodon- 
tidae, with their slightly deepened, laterally compressed bodies, appear to have been 
active mid-water or pelagic predators. The Eurypholidae, on the other hand, with 
their lean, shallow, slightly dorso-ventrally compressed bodies, were probably 
bottom dwellers. The great expansion of the cleithra ventrally in the Eurypholidae 
possibly offered a protection against abrasion. In Ewurypholis boissiert and 
Saurorhamphus freyert the ventral edge of the mandible is strongly inclined medially 
and the mandibular sensory canal is enclosed within a tube for most of its length. 
In the Enchodontidae no such medial inclination of the mandible occurs and the 
sensory canal is housed in a shallow groove. Thus in the Eurypholidae both throat 
and sensory canal are protected from abrasion. The pelvic fins in the Eurypholidae 
are sub-thoracic and enlarged and possibly these may have served as supports on 
which the fish rested on the bottom. This last fact, that of waiting for the prey, is 
in part substantiated by the leanness of the body indicating some muscular reduction. 
Additional components of the sensory canal system on the dorsal surface of the 
Eurypholidae probably increased the perceptiveness to stimulation from above. 
Gosline, Marshall and Mead (1966 : 7) have considered a similar aspect in relation to 
the frontal commissure of the supraorbital canals in the Myctophiformes. In no 
other teleosts, living or fossil, can I find a mid-dorsal sensory canal like that of the 
Eurypholidae. 
