No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 575 
In Chimaera and in Callorynchus there is a muscle, called by 
Vetter the levator anguli oris, which lies below and in front of 
the eye, immediately superficial to the adductor mandibulae. 
The anterior part of this muscle arises as a thin, broad tendon 
above and in front of the eye. It contracts immediately to a 
smaller tendon, and then, becoming muscular, separates into 
two portions and is inserted by round tendons on the adjoin- 
ing ends of the maxillary and mandibular cartilages (No. 125, 
p. 441). The posterior part of the muscle arises from the 
lower edge of the orbit, and is inserted by a very slender ten- 
don on the mandibular cartilage and in the skin at the corner 
of the mouth. Vetter gives the innervation of both divisions 
in Chimaera by branches of the inferior maxillary, but his 
figure seems to show that the anterior division of the muscle is 
innervated by a branch of the superior maxillary, which nerve 
supplies also the labialis anterior. In Callorynchus both divi- 
sions of the muscle, and the labialis anterior also, are said by 
Stannius to be innervated by the superior maxillary (No. 116, 
p. 46 and Fig. 1, Pl. 1). This want of agreement in the two 
descriptions strongly suggests the error to which Vetter has 
himself called especial attention (No. 125, p. 495, Note 1): 
that of not tracing a nerve or the branch of a nerve to its 
origin, and leads one to infer that the three muscles are inner- 
vated by a nerve corresponding to the r. ad musc. levator max- 
illae superioris in Amia, and hence that they correspond to the 
four divisions of the musculus levator maxillae superioris of 
Amia ; the labialis anterior, probably, to the fourth division of 
that muscle; the anterior division of the levator anguli oris, 
with its double insertion, to the third, which is frequently 
double through part of its length in Amia; and the posterior 
division, which is inserted in part in the skin at the corner 
of the mouth, to the second and first divisions in Amia, the 
former of which in Amia has in part this same attachment. 
The position of the levator anguli oris superficial to the adduc- 
tor mandibulae is naturally suggested by the arrangement found 
in Galeus, where AddB lies in part superficial to Add. 
In Acipenser the large and powerful protractor hyomandibu- 
laris is considered by Vetter the homologue of the levator max- 
