534 
CAPTAIN E. W. SHANN ON 
by the above-noted myocommata form a series of concentric cones. In all, five such 
series of cones occur (C 1-5), of which the dorsalmost have their apices directed 
forwards, the next have their apices directed backwards, and so on in alternate order. 
This is clearly seen in the well-known diagram of Scyllium canicula in Marshall and 
Hurst’s Practical Zoology ; but the completeness of the division at the horizontal 
septum is not adequately brought out, nor is the position of the lateral-line nerve 
indicated. This occupies the furrow between the third and fourth series of cones. 
The directions taken externally by the myocommata are manifestations of the internal 
conformation. • There is an apparent incongruity in that, though three series of 
In the lateral view the deep portion of the l.d. muscle, which, owing to the obliquity of the so-called “horizontal septum, ” 
underlies the l.v. muscle, is shown by shading in the two posterior myomeres. 
C 1-5. Muscle cones : 1, concave ; 2, convex, 
and so forth alternately. 
l.d. Latero-dorsal muscle. 
l.l. Lateral line. 
l.v. Latero- ventral muscle. 
m.d. Mesio-dorsal muscle. 
m.v. Mesio-ventral muscle. 
complete cones are seen in section in the dorsal moiety, only two and a half cones 
appear in corresponding areas on the surface. This incongruity is explained by 
the fact that the ventral moiety overlaps the dorsal to a certain extent ; if the 
ventral moiety be dissected away from the dorsal, the myocommata of the latter 
are found to take a sharp bend backwards in the hidden area, thus completing 
the superficial manifestation of the third, anteriorly directed, series of cones (see 
text-fig. l). 
Let us now trace these muscles forwards to their insertions. The series of cones 
are indissolubly connected up to their insertion on the skull, though the upper two 
were designated mesio-dorsal (M.D.) and the lower one latero-dorsal (L.D.) portions 
respectively of the lateral muscle by Humphry (51), who distinguished them by the 
directions of their superficial fibres. While agreeing with Maurer (Morjph. Jahrb., 
