908 THE AMERICAN NATURALIST. | (Vor. XXXIX. 
prominent there as here. Tiesing, basing his opinion on the 
work of Vetter upon Heptanchus, has regarded these fibers as 
a deeper layer of the constrictor but Acanthias shows this not 
to be tenable. There is no resemblance to a constrictor. In 
the case of the fourth arch the corresponding fibers extend into 

Fic. 9.— Dorsal view of gill arches of Acanthias to show the interarcuales. £, groove ; 
Intarc 1-4, interarcuales ; Ss, subspinalis. 
tough tendons connected with the coraco-arcualis communis mus-. 
cle (Fig. 3). On the dorsal side there is but one instance of 
this extension of the interbranchials (Fig. 6, at the inner poste- 
rior angle of Csd6). A few fibers take their origin from the 
sides of the first vertebra. This could not be considered a 
constrictor. 
Levator Maxillae Superioris. 
Acanthias. 
This muscle (Figs. 2, 11, 14, Lms), already mentioned in con- 
nection with the first dorsal constrictor, árises in common with 
it from the lateral surface of the cranium just posterior to the 
