G64 
SCANDINAVIAN FISHES. 
outside the hyomandibular bone and is united above 
to the inferior margin of the suborbital bones. The 
obliquely ascending branch of the symplecticum, on the 
other hand, is separated by a space, occupied by the 
masticatory muscles, from the two posterior suborbital 
bones, which bound the orbit below, but is united to 
the hind superior corner of the anterior suborbital (the 
preorbital) bone, where the latter meets the lateral 
ethmoid bone. The foremost suborbital bone forms the 
greater part of the side of the snout, being united in 
front as a covering bone to the ento-(meso-)ptery- 
goideum and the quadrate bone, but leaving behind the 
latter an opening in the middle for about a third of 
the depth of the snout; the middle suborbital bone is 
united below to the symplecticum; the hindmost sub- 
orbital bone both to the symplecticum and, behind, to 
the preoperculum. We refer to the opercular apparatus 
a narrow, lancet-shaped, thin bone which lies along the 
inside of the horizontal, forward branches of the pre- 
operculum and the symplecticum and the horizontal, 
backward branch of the quadrate bone. This lancet- 
shaped bone is united by ligaments behind to the upper 
part of the ceratohyoid bone and in front to the an- 
gular part of the lower jaw. The latter union clearly 
shows that the bone must be an interoperculum 0 , cor- 
responding most nearly in form and position to the 
interoperculum in Tetrodon for example, though here 
it lias passed within the symplecticum and become united 
behind to the upper part of the outside of the cerato- 
hyoideum, instead of retaining its union to the sub- 
operculunT', which is here reduced to an extremely 
thin disk within the lower margin of the operculum. 
The lower jaw is remarkable for its extraordinary 
depth behind and its sharply curved and toothless dental 
part. The maxillary bones are comparatively well- 
developed and their hind (lower) extremity is expanded; 
but the toothless intermaxillaries are small, styliform, 
and without nasal processes. The palatine bones are 
shorter than the maxillaries and of fairly uniform 
breadth. At the anterior angle of the union of each 
palatine bone to the top of the ascending branch of the 
“ J. Playfair McMurrich {On the Osteology and Development 
(Oct. 1883), p. 623), assumes that this bone is a metapterygoid. 
b See, however, below, on the ligamentous connexions between 
in Silurus. 
c See for example our figure of Syngnathus acus. The ent 
tuberance on the throat just behind the perpendicular from the eye 
body, B ) the urohyoid bone extends back from the ceratohyoid bones 
d Anatomisk undersokning dfuer ndgra delar af Syngnathus A 
quadrate bone we find the narrow pterygoid bone, which 
is bent at an obtuse angle, and behind the said union, 
close to the ridge of the snout, the entopterygoid bone, 
which is united in the same manner to the quadrate 
bone. 
The tongue is wanting, and the glossohyoid bone 
can hardly be discerned; but the urohyoid bone is com- 
paratively long. When the last bone is drawn back, 
the anterior (lower) end of the ceratohyoid bone with 
the tip of the whole branchial apparatus is forced down- 
wards", the cavity of the mouth being thus widened 
and filled with a fresh supply of water. In this manner 
the Lophobranchs pump in their food together with the 
water needed for their respiration. The method in 
which the transverse dermal folds {vela) just behind the 
jaws assist to this end, has already been touched upon. 
The gill-rakers are small, denticulate, and pectinately 
arranged along both margins of the inside of the branchial 
arches. Their function, the prevention of food and fo- 
reign substances from penetrating into the gill-cavities 
when the lish swallows, has already been pointed out 
by Retzius''. 
The intestinal canal (tig. 170) is simple in all the 
Lophobranchs, but shortest in the Syngnathince. In the 
Hippocampince (the Sea-horses) the intestine forms at 
least a few curves, but in the Syngnathince it is straight 
or nearly so, thus rendering the whole digestive canal, 
from the pharynx to the vent, equal in length to or 
only slightly longer than the abdominal cavity. The 
lines of demarcation between the oesophagus, the sto- 
mach, and the intestine are only internal, and consist 
merely in the difference of the mucous membrane, 
while the beginning of the last division is marked as 
usual by the mouth of the gall-duct. But the small 
intestine is divided from the rectum by an annular 
valve. No pyloric appendages can be traced. The me- 
senterium is wanting or only partly developed, in front 
and behind, to bind the stomach and intestine to the 
dorsal wall of the abdominal cavity. Both the ovaries 
and the testes are paired, simple, and elongated. Their 
discharging ducts are short and distinct down to their 
of Syngnathus Peckianus — Quart. Journ. Micr. Sc., u. ser., No. XCII 
os epihynle , the interoperculum, and the angular part of the lower jaw 
re figure (.4) shows the ceratohyoid bones depressed to a pointed pro- 
; and in the lower figure (the anterior part of the ventral side of the 
and between the opercula. 
cus och Opludion, Vet. Akad. Handl. 1833, p. 146. 
