LATERAL MUSCLE IN TELEOSTEI. 321 
and, being deeply seated, are not visible superficially. Moreover, 
the apices of the superficial cones are of necessity situated in a 
higher horizontal plane than those of the true cones. 
The five longitudinal portions of the lateral muscle which 
MecMurrich (7) derived from his investigation of Amiwrus are 
equivalent to various areas described by previous authors. This 
is indicated by the positions which they take in the above table. 
‘he author implies that the classification is only of empirical 
value. His divisions are based upon the superficial appearance 
of the muscles, and upon the extent of their origins. He does 
not recognise a clear division beneath the lateral line, nor is 
there any suggestion of stratification in any portion of the lateral 
muscle. 
Maurer (6) divides the lateral muscle into two portions, a 
dorsal and a ventral, separated by the lateral line. The dorsal 
portion is outside the sphere of his investigation, the ventral he 
proceeds to spht into layers. 
If the red fibres * immediately ventral to the lateral line be 
removed, a stout muscular layer is observed whose fibres run 
obliquely, from forwards and upwards to backwards and down- 
wards (7. e. in theSame direction as those of the obliquus externus 
of Amphibia). The outermost layer of this muscle runs from 
septum to septum, the inner from rib to rib; since, however, the 
direction of the fibres does not change, the two layers are regarded 
as comprising a single muscle, the obliquus externus 7. 
Ventrally the origins of the fibres of this muscle change so as 
to resemble those of the obliquus internus of Urodeles t, while 
the fibres which meet in the mid-ventral line their fellows of the 
opposite side go to form a rectus. 
Returning to the area of the ventral muscle immediately below 
the lateral line, where the fibres take the direction of the obliquus 
externus of Amphibia, if the superficial fibres be removed a deep 
layer is found whose fibres slant in the opposite direction (Ge. @s 
from forwards and downwards to backwards and upwards, like 
those of the obliquus internus of Amphibia), These fibres form 
a thin deep stratum running from rib to rib§. There is no 
mention, however, of a fascia separating the deep from the super- 
ficial stratum. 
Beneath the above layers is yet a third, in Chondrostoma, at 
least ; this is spoken of as a thick one covering the peritoneum jj. 
The rectus is not, he says, developed as a costal muscle, rather 
as a ventral part of the primary belly-musculature 4. 
* The occurrence of these red fibres is more fully described on p. 326. 
+ The equivalent of Humphry’s latero-ventral (surface) portion. 
+ This and the superficial layer of the next form the “‘ pectoralis ” of Humphry. 
§ Equivalent in all respects to Humphry’s “ obliquus internus.” 
|| This is apparently equivalent to the transversus stratum which Humphry 
observed in the Bream and Dace. Nevertheless, Maurer states that the transversus 
properly so called is absent in all fishes. 
4 From which I gather that this muscle is regarded as being continuous dorsally 
both with the obliquus externus and with the obliquus internus. It thus included 
the “rectus ”’ and ventral portion of “‘ pectoralis” of Humpliry. 
