352 
EDWARD PHELPS ALLIS. 
continuous muscle-sheet, from the lateral edges of a strong 
median fascia which is attached posteriorly, On either side, to 
the lateral edge of the ventral portion of the shoulder-girdle. 
This fascia extends anteriorly, beyond the united ventral 
ends of the shoulder-girdles, as a narrow median tendinous 
band, and, lying close against the ventral surface of the peri- 
cardial membrane, forms, with that membrane, the related 
ventral portion of the wall of the pericardial chamber. The 
fascia is apparently formed in large part by the tendons of 
origin of the fibres of the muscle-sheet, and from there the 
fibres run at first antero-dorso-laterally and then antero- 
dorso-mesially, thus encircling and enclosing the pericardial 
chamber and the truncus arteriosus. The musculi coracc- 
branchiales of the third to the sixth branchial arches thus 
have every appearance of having been developed in intimate 
relations to the wall of the pericardial chamber, and of having 
retained their relations to that wall. The first and second 
coracobranchiales have become more or less independent of 
the pericardial wall and its related fascia. In this fish, as in 
Heptanclius, the deeper and distal portions of the ventral 
ends of the constrictores superficiales both coexist with the 
coracobranchiales. 
The coracobranchiales of Chlamydoselachus are all inner- 
vated, as they are said by Vetter to be in the fishes examined 
by him, by a large nerve of spinal or spino-occipital origin, 
the exact origin and composition of which I have not as yet 
determined, this nerve also innervating the musculi coraco- 
arcualis communis, coracohyoideus, and coracomandibularis. 
This common innervation of these several muscles, their 
practical continuity in the adult Heptanchus, and the fact 
that, in Heptanchus, Chlamydoselachus, Scyllium, and 
Mustelus, coracobranchiales, innervated by spinal or spino- 
occipital nerves, coexist with both the deeper (proximal) and 
the distal fibres of the ventral portions of the constrictores 
superficiales, all of which latter muscles are innervated by 
branchial nerves, give every reason to believe that both 
Dohrn and Edgeworth have in some way misinterpreted the 
