Lava-Flow Fishes — Gosline 
377 
Fig. 2. Right suspensorium, mandible, and opercu- 
lar bones of Snyderidia, from inside. Interosseous 
areas hatched, an, Angular; ar, articular; de, dentary; 
hy, hyomandibular; io, interopercle; li, ligament be- 
tween angular and interopercle; ms, mesopterygoid 
and ectopterygoid; mt, metapterygoid; op, opercle; 
pa, palatine; pp, preopercle; qu, quadrate; so, sub- 
opercle; sy, symplectic. 
to the interopercle (Fig. 2), came free from the 
rest of the jaw. Presumably it was loosely con- 
nected by ligament with the articular, rather 
than united with it by suture as in the other 
ophidioids available. 
Visceral arches: The hyoid apparatus of Sny- 
deridia seems to show no unusual features. 
There are seven branchiostegal rays: five on the 
ceratohyal and two on the epihyal. The urohyal 
is short and has the configuration of an inverted 
T. 
The first gill arch in Snyderidia contains two 
rows of spinous patches. The outer row below 
contains about 13 spinous patches in front plus 
three elongate struts; the uppermost of these is 
at the angle. Each of these struts, i.e., developed 
gill rakers, has a whole series of spinelets pro- 
jecting from its inner surface. On the upper 
portion of the gill arch ( above the angle ) there 
are 3 patches of spinelets in the outer row. 
The basibranchial area between the bases of 
the 2nd gill arch and the pharyngeals consists of 
an elongate raised ridge with teeth. There are 
basibranchial teeth in some brotulids (cf. Gos- 
line, 1934: 77, fig. 3), but none are present in 
those for which skeletons are available. The basi- 
branchials of Otophidium are also toothless, but 
Emery (1880, pi. 5) shows basibranchial teeth 
in tf Fierasfer acus.” 
In Snyderidia there are the usual pair of sepa- 
rate toothed lower pharyngeals and three pairs 
of toothed upper pharyngeals. 
Regan has used the gill membranes as a char- 
acter for separating most of the brotulids from 
the carapids (Table 1, no. 3). In Snyderidia 
Gilbert (1905: 654) states: "Gill-openings con- 
tinued forward to below eye; gill membranes 
separate, free from isthmus.” In this feature, and 
Pyramodon is similar, Snyderidia belongs with 
the brotulids. 
Pectoral girdle and fin: The bones of the pri- 
mary pectoral girdle are very light and difficult 
to make out. Apparently they are similar to those 
drawn for "Fierasfer” by Emery ( 1880, pi. 4, 
fig. 35 ) . The coracoid and scapula are in contact, 
and there is a small scapular foramen. 
Regan differentiates the Brotulidae from the 
other two ophidioid families in having the cora- 
coid and scapula separated by cartilage. This is 
certainly true of Brotula. However, in Dine- 
matichthys the scapula and coracoid seem to be 
nearly in contact (Fig. 3 h) . Be that as it may, 
the primary pectoral girdle is so poorly de- 
veloped in all the ophidioid skeletons available 
that it would seem inadvisable to attach much 
importance to differences between them. 
In the secondary pectoral girdle, Regan has 
used the structure of the posttemporal as a 
character for distinguishing families (Table 1, 
no. 9) • However, the distinctiveness of the post- 
temporal structure as stated by Regan is greater 
than in the fishes. Whether the lower post- 
temporal limb articulates directly or by ligament 
with the opisthotic is difficult to determine in 
available skeletons; in all, the tip of the lower 
limb of the posttemporal closely approaches the 
opisthotic, but even in Brotula the main attach- 
ment between the two bones appears to be 
ligamentous. 
There is indeed considerable differentiation 
among the relative sizes of the two posttemporal 
wings in the skeletons at hand. In Brotula both 
prongs are about equally long; in Otophidium 
the upper prong is nearly five times as long as 
the lower (Fig. 3 a); the other brotulids and 
Snyderidia fall between Brotula and Otophidium 
in the relative lengths of the posttemporal wings. 
Vertebral column: The vertebral column has 
perhaps been used more than any other internal 
structure in differentiating groups of ophidioid 
