5/2 ALLIS. [Vou. XII. 
forms a distinctly separate muscle lying in front of and over- 
lapping externally the main muscle. It is tendinous above, the 
long, somewhat slender tendon running forward and becoming 
muscular again before its insertion, as a short, stout muscle body, 
on the anterior wall of the orbit immediately below the inser- 
tion of the obliqui muscles. In Galeus the tendon connecting 
these two portions of the muscle is short, and the stout, orbital 
muscle-body lies imbedded in the remaining lower portion of 
the muscle, with which its fibres are in part directly contin- 
‘uous. That part of the lower portion of the muscle that lies 
immediately posterior to the tendon of the upper portion, has 
its origin from the upper edge of the cartilage of the upper 
jaw ; that part that lies in front of the tendon has its origin, in 
part, from the front wall of the orbit and, in part, it extends for- 
ward on the under side of the head towards the middle line of 
the body, having its origin there. The outer fibres of the lower 
portion of the muscle become tendinous posteriorly, the tendon 
being in part continuous with a fascia covering the outer sur- 
face of the adductor and extending to the hind edge of the 
lower jaw, and in part continuous with a tendinous formation 
extending into the adductor from its outer surface. The deeper 
fibres of the muscle are continuous with the fibres of the 
deeper part of the adductor. A somewhat similar arrangement 
is found in Acanthias and Scymnus, but the separation of the 
muscle from the main adductor seems to be more complete 
than in Galeus, and the tendon in its lower posterior portion 
more developed. The muscle is, however, considered by Vetter 
a part of the adductor and is called by him Add. The corre- 
sponding muscle in Mustelus is called by Tiesing the levator 
labii superioris. 
In Heptanchus the special innervation of that part of the 
adductor that corresponds to AddB is not given by Vetter. In 
Acanthias and Scymnus, he says, that it is innervated by a 
branch of the r. maxillaris superior trigemini, but Stannius 
(No. 116, p. 46) finds the corresponding muscle in Spinax, and 
Tiesing (No. 123, pp. 86 and 96) the corresponding muscle in 
Mustelus innervated by a branch of the r. maxillaris inferior 
trigemini. In the three fishes described by Vetter the levator 
