LOPHOBRANCI-IS. 
665 
A: Male, witli the abdominal wall opened and folded outwards and the 
marsupium, in which appear the cavities left by the eggs, distended. 
h, liver; va, air-bladder, with the anterior, thin-walled part pointed 
and obliquely divided from the posterior; t, testes; pa, anal fin; vu, 
urinary bladder; i, intestine, opened for a short distance at the vent; 
ug, urogenital aperture, behind (below) the vent, which is opened. 
B: Female, with the abdominal wall opened and folded outwards. 
/), liver; vf, gall-bladder; pa, anal fin; 7,, intestine, at the mouth of 
the gall-duct coming from the right side (in the figure the left); ? 2 , 
posterior part of the intestine, opened in order to show the valve that 
divides the intestine from the rectum, which is also opened as well 
as the vent; ov, ovaries; vu, urinary bladder; tig, urogenital aperture. 
opening just behind the vent. The urinary bladder is 
long and narrow, lies on the left side, and coasts the 
left sexual organ. The air-bladder is large and coasts 
the upper wall of the abdominal cavity for at least 
one-half or two-thirds of the length of the latter. 
The ribs are wanting. Among the other peculiari- 
ties of the skeleton the structure of the shoulder-girdle 
is especially remarkable. The posttemporal bone (fig. 
171, pt) coalesces with the mastoid bone ( epoticum ) of 
the skull and is covered in a Ganoid fashion by a plate- 
like layer, pointed behind. The supraclavicular bones are 
wanting; but the clavicle (cl) is all the larger. This 
bone is T-shaped, with the upper (horizontal) bar united 
to the transverse processes of the first two vertebra?. 
The first transverse process is directed backwards, and 
so long that all the anterior upper branch of the cla- 
vicle may be contiguous with it: while the second of 
these processes, which is comparatively short, and only 
slightly expanded at the top, adjoins the angle between 
the horizontal and vertical branches of the clavicle. The 
outside of the clavicle is covered by the three plates on 
each side of the body which form the first (foremost) 
ring; and in Syngnatlms acus the inner prong of the 
vertical shaft, which is forked at the bottom, in the T- 
form of the clavicle, is supported on the first abdominal 
plate belonging to the same ring. This plate is wanting 
in Syngnatlms typhle , where the support is therefore 
given by the lower lateral plate. Only the anterior 
margin, however, of the middle lateral plate in this ring 
is united to the middle of the shaft in the T-form of 
the clavicle, the rest of this plate lying as a. covering over 
the muscular mass of the pectoral fin, in the middle of 
which mass we find the extremely thin scapulo-coraeoid 
disk (sc) together with the four basal bones (fig. 171, 
has) of the pectoral fin. This disk is not divided here 
into its ordinary component parts (the shoulder-blade 
and the 'coracoid bone), and is extended between the 
hind part of the upper (horizontal) branch of the clavicle 
and the inner prong of the vertical shaft of the clavicle, 
without touching this bone at any other point. At this 
lower end of the clavicle, however, within the lower end 
of the scapulo-coraeoid disk and above the inner side of 
the first two abdominal plates in Syngnatlms acus , lies 
one interclavicle (id), which meets both the clavicle and 
the said disk (fig. 171, sc). Neither in Syngnatlms acus 
nor in S. typhle have we succeeded in finding more 
than one such interclavicle, though according to Par- 
ker the former species possesses two. 
