GREGORY: FISH SKULLS 407 



Himantolophus and its ally Diceratias would appear to be almost immediately derivable 

 from Oneirodes by the loss of the parietals and the dominance of the supraoccipital and 

 epiotics (Regan, 1926, p. 21). The interfrontal fontanelle is nearly closed. Himantolophus 

 groenlandicus Luetken has an oval body (Fig. 278) and' a thick skin with large scattered 

 bony plates. The teeth are depressible in 3-5 series, the inner largest. The illicium in this 

 species bears several long branching tentacles. In Diceratias of the same family the mouth 

 is upturned. The skull {op. cit., p. 20) has the family characters. Oneirodes eschrichtii 

 of the family Oneirodidse is a rather large fish of oval, rather deep form; it is more specialized 

 than Dolopichthys luetkeni in general appearance, especially in its small eyes, very small 

 pectoral fin and thick rays of the median fins. In a very small fish referred to Oneirodes 

 (Fig. 279) the body is globose and the endocranium but little ossified. The short illicium 

 and its basal rod occupy a deep fossa. 



The "Aceratiidae" are extraordinarily specialized and on the whole have strayed the 

 farthest of all ceratioids away from the ceratioid norm. Parr (1930a) has shown that at 

 least some of the " Accra tiidae" are the dwarfed males of gigantic female ceratioids. In 

 " Aceratias macrorhinus" Brauer the body is almost cylindrical in shape, with vestigial 

 dorsal and anal fins. The large eyes are telescopic and directed forward. The illicium 

 has disappeared, as such, but according to Parr it is represented by three denticles at the 

 tip of the vestigial rostrum. On either side, in front of the bulging eyes, projects a great 

 olfactory capsule with two nostrils, of which the posterior is larger and opens backward. 

 The moderate-sized mouth is horizontal. 



The top view (Fig. 280) of " Haplophryne hudsonius "Beebe (1929) shows that " Haplo- 

 phryne" is already well on the way toward " Aceratias" of Brauer. For its eyes are not 

 small but large, they do not look outward but outward and forward, they already protrude 

 widely from their sockets, the orbits are guarded by a sharp sphenotic spine pointing out- 

 ward and slightly backward. The olfactory sacs with seven olfactory laminae, while not 

 as well developed as those of Aceratias, are precisely in the right position. They have two 

 openings, of which the posterior one faces obliquely backward toward the eye (Beebe, 

 1929, p. 36) fundamentally as in " Acer alias indicus^' (cf. Regan, 1926, p. 45, Fig. 26). 

 The rostral projection bears three denticles, one median and two lateral, much as in 

 " Aceratias indicus." In the side view we note that in "Haplophryne hudsonius" the rather 

 small mouth is nearly horizontal and very low down on the head, much as in "Aceratias 

 macrorhinus." The general form of the body is such as could readily give rise to that of 

 "Aceratias." There are nine caudal rays, as in the latter. 



"Haplophryne" is, however, more primitive than "Aceratias" in certain features 

 besides those noted above: thus it assuredly retains large parietal bones, as does " Rhyn- 

 choceratias," according to Parr (1930f, p. 9), in spite of the fact that according to Regan 

 (1926, p. 42) these elements are absent in the family as a whole. 



" Rhynchoceratias" (Fig. 281) has a large rostral bone, the mechanism of which has been 

 figured and described by Doctor Parr (1930c, pp. 8-11). He has shown that this bone is 

 operated by the basal bone of the illicium, with three pairs of muscles, so that it rocks 

 forward and backward along the hinge-like vomer and rests laterally on the anterior sym- 

 physial processes of the opposite premaxillse; thus its denticles oppose the anterior denticles 

 of the lower jaw; he holds also that this bone is not a mesethmoid and that it occupies the 

 position that a greatly enlarged and ossified illicium would occupy. If, however, the 



