NERVOUS SYSTEM AND SENSF ORGANS OF AMIURUS. 449 



PLATE IV. 



Figs. 1, 2, 3, represent dissections of the fifth nerve of the right side from 

 the roof of the mouth, of which 1 is the most superficial (ventral), 

 and 3 the deepest (most dorsal). To expose the 3rd and 6th nerves 

 and the ramus buccalis, as seen in Fig. 2, it is necessary to cut the 

 superodateral and infero-medial strand, turning forwards the 

 nerves to which they give origin. In Fig. 3 the 3rd and 6th nerves 

 have been removed to show the cutaneous branches of the Rr. add. 

 mand. and buccalis, as well as the branches of the R. ciliaris and 

 opthal. profundus. The dotted lines in Fig. 3 indicate the 

 boundaries of the adductor mandibular, AM; levator arcus pala- 

 tini, LAP ; and dilatator operculi, DO. 



FiO. 4. — Dissection of same nerves represented in Fig. 6 from dorsal surfaces. 

 1. Branch of R. oph. prof, to middle line nose. 2. Along 

 medial border nasal sac. 3. To nasal barblet. 4. Along outer 

 border nasal sac. 5. To fat, &c, in front of eye under origin of 

 lev. arc. pal. 6. Is the chief branch of R. ciliaris. 7. The cut- 

 aneous branch of R. buccalis. 8. Of R. add. mand., with which 

 are connected the muscular branches for lev. arc. pal. and dil. op. 

 9. Branch for muscle of maxillary barblet. 10. For add. mandib. 



Fig. 5. — Diagram of brachial plexus. 



A n , JST*, N 3 , iV*, &c. 1st, 2nd, 3rd, 4th, spinal nerves, of which 

 the first four enter into the formation of the brachial plexus. 

 Description of branches in text. 



Fig. 6. — Diagram of Rr. dorsales and ventrales of the spinal nerves. Two 

 vertebra? are represented by dotted lines. 

 Rmv. Branches for ventral musculature. 



Rmp. & s. Branches from plexus supplying the deep and super- 

 ficial muscles of the anal fin. The infracarinales are supplied by 

 branches similarly derived to those marked E.m.s. 



Fig. 7. — The first 8 vertebrse from the latero-ventral aspect. 



ao points to the aortic canal opposite the point of junction of 

 the 4th and 5th vertebrae, o.o., the oblique, c.o., the cres- 

 centic ossifications referred to in the text. Tr., the transverse 

 processes or costiferous pedicles of the anterior vertebra;. V., 

 VI.. VII., &c. Bodies of the fifth, sixth and seventh vertebrae. 



Fig. 8. — Longitudinal vertical section of adult near middle line. 



I., II. , III., &c. Centra of 1st, 2nd, 3rd, vertebra;. i£.0., exoccipi- 

 tal. B.O., basioccipital. S.O., supraoccipital spine. Sp. III. & 

 IV. Xeural spines of the 3rd and 4th vertebras. 1, 2, 3, 4, &t. 

 Points of emergence of the 1st, 2nd, 3rd, &c, pairs of spinal 

 nerves. Fov., in the fovea sacculi ; directly above it is the opening 

 into the cavum sinus imparis, on the osseous roof of which 1 

 stands. The black spot above BO indicates the apertura interna 

 of the atrium sinus imparis. The membranous roof of the cavum 

 being removed shows the stapes and claustrum in the jjosition 

 indicated in 8a to the right of the figure. 



Figs. 9, 10, 11, 12, 13, are horizontal sections through the cephalic end of a 

 fish of 3-4 cm. in length, of which 9 is the most dorsal. 9 and 10 

 are merely intended to show the relations of the claustral cartilages 

 to the cartilaginous cranium and roof of the spinal canal. 



Fig. 11. — Tz , M. trapezius. Sc. , supraclavicle. Tsc, trans- 

 verse process of supraclavicle. 7V 4 ., transverse process of 4th 

 vertebra. Sp., saccus paravertebralis. Asi., atrium sinus imparis. 



