ON CERTAIN POINTS IN THE ANATOMY OF SIREN 
LACERTINA. 
BY H. W. NORRIS. 
In connection with a study of the distribution of the cranial nerves of 
Siren, the results of -which will be published in the near future, the writer 
found certain features of the general anatomy that seem worth especial 
notice. 
Vaillant (1863) in describing the muscles of the head in Siren men- 
tions “Pabducteur de la machoire superieure,” a small muscle said to 
be inserted in part upon a small bone believed by Cuvier to be a maxilla. 
The writer has not had access to this paper on Siren by Cuvier, but has 
made use of the reproduction of his figures by Hoffman (1878). Fischer 
(1864), Wiedersheim (1877) and ’Wilder (1891) have not been able to 
find either the muscle mentioned by Cuvier and Vaillant or the small 
bone on which it was said to be inserted. Parker (1882) mentions and 
figures two “small seed-like centers opposite the middle of the premax- 
ilLaries” as maxillaries, but he says nothing of muscles connected with 
them. The writer finds in the position described by Parker a minute 
ossification on each side. This may, however, be larger on one side 
than on the other, in fact, is wanting altogether on one side in some 
specimens. Its minute size, and possibly complete absence on both sides 
in some instances, may explain the failure of some investigators to find it. 
It has no muscles connected with it. It .probably represents a maxilla, 
as Cuvier, Vaillant and Parker believed. 
In the lower jaw of Siren Wiedersheim describes three skeletal ele- 
ments, dental e, angulare and meckePs cartilage. Huxley (1878) mentions 
‘ 1 a dentigerous splenial element. ’ ’ Parker describes a splenial as “a very 
delicate, styliform, dentigerous splint.” Gadow recognizes a splenial in 
Siren, but says that “with the exception of small teeth on the vomer the 
mouth is toothless.” The writer finds the operculare (spleniale) as de- 
scribed and figured by Parker, and formed chiefly by the fusion of the 
bases of teeth. 
The writer (1908) described in Amphiuma two muscles having their 
insertion upon the antorbital cartilage and innervated by a twig of the 
