CLASSIFICATION OF DEVONIAN FISHES 433 
stress upon it. Nevertheless, the skull and scales of J/egalichthys 
accord so closely, both histologically and morphologically, with those 
of the better known Saurodipterines, that I entertain little doubt 
as to its real place in the latter family. 
Megalichthys has two principal, many lateral, jugular plates ; 
and a single rhomboidal, azygos plate is placed between the 
anterior ends of the two principal jugulars. Between the upper 
margins of the opercula and in the upper occipital region, lie three 
bony plates, whose signification Professor Agassiz considers to be 
“somewhat enigmatical,” but which really correspond exactly 
with the three bones which occupy the same position in the 
Glyptodipterini and Saurodipterinii What Agassiz terms the 
frontals are certainly the long parietals, whereas those which 
he calls “ethmoids” are the frontals. His “moignon intermaxil- 
“laire” is a crescentic shield, which terminates the head ante- 
riorly, and presents distinct indications of a division into a 
number of pieces; the contour of the proper premawillary portions, 
separated by a median suture, which form the lower and anterior 
boundary of the shield, being very well defined. The other parts 
entering into this shield represent, I believe, the prefrontals and the 
ethmoid. Ifit were amalgamated with the frontals and these with 
one another, we should have an almost exact reproduction of the 
anterior cranial buckler of Osteolepis. In a well preserved specimen 
of the skull of Alegalichthys before me, the orbits are small circular 
cavities, placed at about the junction of the anterior and middle thirds 
of the head. They are bounded, in front and below, by a small tri- 
angular bone (like a lachrymal) as in Polypterus; below, by a small 
part of a large suborbital bone, whose anterior margin joins the 
premaxilla and its inferior margin the maxilla; below and behind, 
by another suborbital bone, fitted in between the preceding, the 
maxilla, and a postorbital bone. The mawilla, large and long, is 
narrow anteriorly, where it abuts upon the bone termed “ pre- 
operculum” by Agassiz; like the premawilla, its edges are beset 
with small teeth. Agassiz says, “Le coté antérieur du mufle est 
“élégamment échancré au milieu et renflé en un bec, tres obtus, 
“qui porte dans notre exemplaire une grosse dent canine,” and on 
making a transverse section of a Mlegalichthys snout I found a 
median, stout, backwardly projecting ridge of bone, containing two 
large alveoli, one on each side of the middle line. The one of 
these alveoli exhibits the section of the base of a large tooth 
with greatly folded dentine. 
While the exoskeleton of Alegalichthys is exceedingly similar to 
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