LATERAL MUSCLE IN TELEOSTEI. 327 
the case in some other Teleosteans, but in the majority which I 
have examined a small bundle of fibres, undoubtedly the con- 
tinuations of the latero-ventral portion, are attached to the upper 
extremity of the cleithrum. At its point of attachment and for 
a short distance behind, the latero-ventral portion is actually 
severed from the mesio-ventral; though, further back, the two 
are continuous, just as are the mesio-dorsal and latero- dorsal 
portions. With the decrease in width of the latero-ventral 
portion, the mesio-ventral portion increases so that it becomes 
attached to the whole length of the cleithrum, except at the 
dorsal extremity of that bone, and to the coracoid in part. There 
exists, however, a triangular area, composed of connective-tissue 
traversed by a few muscle fibres, beneath the pectoral fin ; this 
triangle has its base on the cleithrum, consequently there appear 
to be two main insertions of the mesio-ventral portion on the 
cleithrum. 
On the ventral surface in the anterior region the fibres of the 
mesio-ventral surface meet their fellows of the opposite side ; 
the fibres are here arranged parallel to the long axis of the body, 
which has led some authors to regard them as homologous 
(Humphry and Maurer), or, at least, analogous (Wiedersheim) 
to the rectus abdominis of the higher vertebrates. In Teleosteans 
whose pelvic fins are thoracic or jugular in position the rami- 
fications of this portion of the lateral muscle show remarkable 
variety. To describe these ramifications in detail would only 
serve to confuse the issue of the investigation in hand; but 
it is worthy of note that, m every example which I have had 
occasion to examine, a bundle of fibres from the mesio-ventral 
portion of the lateral muscle runs forward without interruption 
to be inserted on the hypohyal. 
Knauer (5) figures the lateral muscle of the Gurnard im the 
area just behind the shoulder-girdle (Pl. ui. fig. 20). In this 
illustration the mesio-ventral portion (Bauchmuskel) is depicted 
as gradually disappearing towards its posterior extremity, and in 
the text he says that in the anal region this muscle, with its 
straight-running fibres, is reduced to a small strip on either side ; 
further, that these strips fuse with the latero-ventral portions 
(Riickenmuskulatur) behind the anus. This is not indicated in 
the figure, where the mesio-ventral portion appears to die out 
in the anal region; Jrigla, however, with its flattened ventral 
surface is not, perhaps (with deference to the author), the best 
type of Teleostean fish for representing in side view the entire 
extent of this portion of the lateral muscle. A little distance 
behind the anus the mesio-ventral portion entirely disappears, 
and the latero-ventral portions (schrigen Riickenmuskel) of 
either side are separated by the anal fin. I had also used 
Gurnards* in my investigation of the lateral muscle. Since 
reading Knauer’s paper, I have examined them again most 
* Trigla gurnardus, whereas Knauer’s specimen was 7’, hirundo. 
