92 
PACIFIC SCIENCE, Vol. XVII, January 1963 
upper of which articulates with the skull. In 
Bleekeria a similar break in the circumorbital 
ring occurs, but it is shorter than in Ammo- 
dytes and the posterior series seems to contain 
three or four small elements instead of two. 
Hypoptychus has the same two anterior ele- 
ments followed by a broad gap; posteriorly, 
however, there is only a single ossicle, and it 
is fused to the sphenotic. 
None of the six fishes have any subocular 
shelf from the circumorbitals. 
JAWS: In sand-diving fishes like Ammodytes 
the mouth is usually not terminal; either it is 
withdrawn below an overhanging snout, as in 
Crystallodytes, or protected by a prognathous 
chin, as in Ammodytes. In Ammodytes the 
leading, lower jaw is firmly attached, but the 
upper has developed excessive powers of pro- 
trusion when the mouth is opened (van Dob- 
ben, 1935: 34-36). The great protrusibility of 
the upper jaw in Ammodytes is accompanied 
by a weakening of the bony elements, and it 
is probably in relation to this that Ammodytes 
and Bleekeria have edentulous premaxillaries. 
So far as jaw structure is concerned, Hypopty- 
chus is intermediate between the normal per- 
coid type and the specializations found in Am- 
modytes and Bleekeria. 
The premaxillary of Ammodytes (Fig. 3 a) 
consists of a long pedicel movably articulating 
at its base with the remaining portion of the 
premaxillary. The distal half of the maxillary 
tapers gradually to a point (Fig. 3 a). The upper 
jaw of Bleekeria is essentially similar to that 
of Ammodytes except that a number of small 
ossicles are to be found in the ligamentous 
tissues connected with the jaw apparatus. Thus, 
there is an ossicle above the more lateral of the 
two pedicels of the premaxillary, another at 
the distal end of the premaxillary, and a whole 
series in the ligamentous tissue that runs be- 
tween the upper and lower jaws. 
The upper jaw of Hypoptychus (Fig. 3 b) 
differs from those of Bleekeria and Ammodytes 
in the following features: the premaxillary 
bears a row of teeth (there are about 14 conical 
teeth in a single row on each side, not shown in 
Fig. 3 h)\ the premaxillary is fused to its pedicel; 
and the tip of the maxillary is expanded distally. 
A movable articulation between the pre- 
Fig. 3. Head skeletons of ammodytoids: superior 
views, with the premaxillary somewhat protruded, of 
a, Ammodytes tobianus, and b, Hypoptychus dybow- 
skii; lateral view, c, of cranium of Ammodytes tobi- 
anus. ba, Basisphenoid; bo, basioccipital; ca, cartilage; 
co, circumorbital; eo, exoccipital; ep, epiotic; fr, fron- 
tal; ha, anterior hyomandibular socket; hp, posterior 
hyomandibular socket; in, intercalar; la, lacrimal; le, 
lateral ethmoid; me, mesethmoid; mx, maxillary; na, 
nasal; pa, palatine; pc, prootic; pi, pleurosphenoid; po, 
posttemporal; pr, parietal; ps, parasphenoid; pt, ptero- 
tic; px, premaxillary; so, supraoccipital; sp, sphenotic; 
tb, tabular; tf, trigemino-facial foramen; and vo, 
vomer. In the superior view of Ammodytes, a, the 
epiotic is covered by the posttemporal. 
maxillary and its pedicel is also found in Crys- 
tallodytes, as well as in blennioids such as 
Cirripectus and Istiblennius. In Parapercis and 
Tripterygion, which have strong premaxillary 
teeth, the pedicel is stout and fused to the 
toothed portion. 
gill covers: In Ammodytes (Fig. 4b) and 
Crystallodytes (Fig. 4c) the subopercles are ex- 
panded, presumably to protect the throat region. 
Indeed, the lower border of the articular in 
Crystallodytes is greatly expanded below as well 
(Fig. 4c). 
SUSPENSORIUM: The suspensorium of Am- 
modytes is specialized in a number of regards 
(Fig. 4b). Most notable among these is the 
elongated palatine strut. The whole length of 
this strut from its forward tip to its articulation 
with the quadrate is made up of the palatine 
