312 
EDWARD PHELPS ALLIS. 
by Edgeworth, as by Fiirbringer, the interbasalis. This term 
I shall also employ in the following descriptions and dis- 
cussions, the other two muscles being called the arcualis and 
the interarcualis. The term interbran chialis ” is said by 
Edgeworth (loc. cit., p. 232) to be employed by him as 
Vetter employed it, and it is said to lie wholly proximal to 
the constrictor superficialis. 
Dohrn does not specify to what particular fishes his 
several observations apply, classing them all under the 
general term “ selachians ” ; but the figures that accompany 
his work are of Scyllium, Pristiurus, and Torpedo. Edgeworth 
limits his observations on the Plagiostomi definitely to 
Scyllium, but in his generalisations he considers them to 
apply to all the Selachii, and apparently also to the Batoidei. 
As both authors included Scyllium in their investigations it 
is instructive to note certain marked differences in their 
observations. According to Dohrn the dorsal end of each 
branchial myotome gives origin both to a dorsal portion of 
the constrictor superficialis and to the interarcuales dorsales 
of the related arch. According to Edgeworth a dorsal 
portion of the myotome of each arch is first cut off to form 
the musculus trapezius, and it is from that portion of the 
myotome that lies ventral to this dorsal portion that the 
musculi constrictor superficialis and arcualis (interarcuales, 
Dohrn) are developed. Dohrn accordingly entirely over- 
looked the separation of the trapezius from the dorsal ends 
of the several branchial myotonies, which would certainly be 
a serious oversight on the part of so careful a worker. 
According to Dohrn the interarcuales dorsales I are derived 
from the branchial myotonies, while, according to Edgeworth, 
they are of spinal origin. According to Dohrn the con- 
strictor superficialis of each arch lies dorsal to the inter- • 
bran chialis, or possibly both dorsal and ventral to that muscle, 
and it is definitely said that it does not traverse the branchial 
diaphragm. Accordiug to Edgeworth it is primarily limited to 
the branchial diaphragm, there lying distal to the inter- 
bran chialis ; it has no dorsal, levator prolongation and never 
