260 MR. ST. GEORGE MIVART ON [Apr. 22, 
sheet from the region of the heart backwards to the inside of the 
pelvis. It does not seem to extend so far inwards towards the 
middle line of the body as does the internal oblique. 
The abdominal nerves pass along between this muscle and the in- 
ternal oblique. 
Rectus. This muscle consists, as usual, of antero-posteriorly 
directed fibres in the middle of the abdomen, but is very difficult 
accurately to define. It seems to be overlapped externally by some 
of the fibres of the external oblique, while internally it is closely 
adherent to what is either a deeper portion of the rectus or the 
median part of the internal oblique, and which runs forwards (with 
the scapular arch, except the sternum, altogether superficial to it) 
to be inserted, as before said, into the basihyal. ‘The external por- 
tion of the rectus is inserted anteriorly into the sternum, posteriorly 
into the anterior part of the pelvis. 
Retrahens costarum. ‘This elongated muscle passes antero-pos- 
teriorly, on each side of the spine, beneath the bodies of all the 
trunk-vertebrze, being attached to them and to the ribs down to 
their extremities, where it is closely connected with the fascia of the 
transversalis. The muscle gets thinner and smaller backwards, and 
appears to end at the commencement of the caudal region; but 
anteriorly it enlarges and passes, as a fleshy mass, beneath the skull. 
Throughout the trunk this muscle is separated from the dorso-lateral 
muscular mass by the internal oblique and transversalis ; but where 
these diverge from that mass to leave space for the branchial arches, 
there the muscle now described becomes applied to the under surface 
of the dorso-lateral mass, and more or less closely connected with it. 
MuscuLes oF THE HEap. 
Temporalis, his (fig. 1, 7.) is the most anterior of all the 
muscles on the dorsal aspect of the body, its anterior margin even 
extending forwards in front of the eyes. It is not a completely 
distinct muscle, as its hinder end is but imperfectly separated from 
the innermost part of the dorsal lateral mass of the same side; of 
which it, in part, may therefore be considered the extreme anterior 
prolongation. It also takes origin, by fascia, from the first three 
neural spines and from the anterior part of the upper surface of the 
skull—Cuvier’s frontal. The most anterior fibres slope backwards ; 
but all converge, and passing behind the eyeball, are ultimately at- 
tached, by means of a strong tendon, to the inner side of the summit, 
of the mandible just in front of its articulation with the suspensorium, 
and behind and somewhat within the insertion of the masseter. 
The pterygoid. Dr. Fischer* describes this muscle as arising from 
the side of the skull and from the upper surface of the pterygoid, 
and with a similar insertion to the temporal, from which it is very 
indistinctly separable. In my specimen it seems to be so intimately 
united with the temporal that I cannot but doubt its distinctness. 
* Anatomische Abhandlungen iiber die Perennibranchiaten und Derotremen. 
Hamburgh, 1864, p. 63. 
