450 NERVOUS SYSTEM AND SENSE ORGANS OF AMIURUS. 
PLATE IV.—(Continued). 
Cl., claustrum. S., ‘stapes.’ 2, 3, 4, dorsal roots of 2nd, 3rd and 
4th spinal nerves with their respective ganglia. 1 the position of 
the first spinal ganglion which does not appear in this section. 
A,, the arch of the 8rd vertebra. /s., medulla spinalis. Ap., 
Ampulla frontalis. 
Fig. 12.—Th.. thymus. Lb., most posterior of the levatores 
branchiarum. &. lat. vag., points to the root of the vagus in con- 
nection with which is seen the portion of the ganglion trunci 
which gives off the ramus lateralis. Si., sinus impar. or saccus 
endolymphaticus. Csi., in the cavum sinus imparis pointing to the 
osseous lateral wall of the cavum. i., the ‘incus.’ m., the 
‘malleus.’ Asi., points to the atrium sinus imparis, as bounded 
by the spoon-shaped process of the ‘stapes’ s., and lies on the 
thickened patch of dura mater which is seen in vertical section 
in Fig. 14.. I., IL, IIL, IV., stand on the middle points of the 
centra of the Ist, 2nd, 3rd and 4th vertebr. Ab., in the cavity 
of the air-bladder points to its union with the posterior end of the 
malleus. Vcid., vena cava inferior dextra. i 
Fig. 13.—G@c., the gill cavity and its opening on the left side. 
EGc., epithelium of the roof of the gill cavity. De., duct. endo- 
lymph. As., asteriscus in the lag. cochlee. Csi., in the cavum 
sinus imparis points to the basi-occipital and the exoecipital cartil- 
ages resting on it.  G. 1X. & X., ganglia of glossopharyngeus and 
vagus. 
Fies. 14 and 15, are from vertical sections through fish of same age as the 
foregoing horizontal sections, of which 15 is the more anterior. 
(@., esophagus. Jfc., mucous canal in postfrontal. #. lat. V., 
ram. lateralis trigemini. Cp., canalis frontalis. Le., lagena 
cochlee. S., sacculus. Ao., aortz at sides of which are the 
sympathetic ganglia, The sections are slightly oblique, so that the 
right sides represent planes somewhat posterior to the left. The 
thymus is seen on the’one in continuity with the epithelium of the 
gill cavity, on the other its posterior end is seen wedged in between 
the trapezius muscle and the levat. branch. post. 
Additional letters in 14. 
Le., lateral mucous canal in section. Hk., head-kidney. L., 
liver. 2. lat. va., ram. lat. vagi in section as it crosses the 
transverse portion of the supraclavicle. o., Basioccipital. Oc., 
occipital cart., above which is the supraoccipital spine. D.M., 
dorsal musculature attached to the posterior surface of the skull 
on either side of the foramen magnum. 
For additional lettering, see foregoing figures. 
‘Fres, 16, 17, 1$.—The otoliths, sagitta, asteriscus and lapillus, x 6. 
