VISCERAL ARCHES OE THE GNATi IOSTOME FISHES. 
405 
EXPLANATION OF PLATES 21 and 22. 
Illustrating Mr. Edward Phelps Allis's paper on “The 
Homologies of the Muscles related to the Visceral 
Arches of the Gnathostome Fishes." 
Reference Letters. 
Add. Musculus adductor mandibulse. Add. br. I-IV. Musculi ad- 
ductores arc. branch, of I-IV branchial arches, ahy. Afferent artery 
of hyal arch. ap. I-IV. Linear aponeuroses related to the first to 
fourth gill clefts. Arc. I-IV. Musculi arcuales of I-IV branchial 
arches. bcl. I-V. First to fifth branchial clefts. BH. Basihyal. 
bp. 1 V. First to fifth branchial pouches. BR. hy. Branchial rays of 
hyal arch. Care. Musculus coracoarcualis communis. CB. I II. 
Ceratobranchials of first two branchial arches. Cbr. I-V. Musculi 
coracobranchiales of I-V branchial arches. CH. Ceratohyal. Chy. 
Musculus coracohyoideus. Cmd. Musculus coracomandibularis. 
Cs 2 0 . Musculi constrictores superficiales of second to sixth visceral 
arches, ex. I-IV. Extra branchials of I-IV branchial arches, ex. h. 
Extrabranchial of hyal arch. HMD. Hyomandibula. hmf. Nervus 
hyoideo-mandibularis facialis. Ibr^-Q. Musculi interbranchiales of third 
to sixth visceral arches. Ihy. Musculus interhyoideus. Imd. Musculus 
intermandibularis. Ic. Lateral canal of body. Lhmd. Musculus levator 
hyomandibularis. m. Dorsal muscles of trunk. MD. Mandibula. 
mit. Nervus mandibularis trigemini, pc. Pericardial cavity. S. 
Sho ildir-girdle. sp. Spiracle. Tr. Musculus trapezius. vj. Vena 
jugularis. , 
PLATE 21. 
Fig. 1. — Lateral view of the head of a 42-cm. Scyllium canicula, with 
skin removed to show the branchial muscles, x 1L 
Fig. 2. — The same. The constrictores superficiales cut along their 
dorsal edges and turned forward and downward so as to expose the 
underlying structures, x 12 - 
Fig. 3. — Ventral view of the same. The constrictor superficialis of 
the hyal arch cut through in the mid- ventral line and turned forward 
on the right-hand side of the figure. X \\. 
Fig. 4. — The same ; a deeper dissection. On the left-hand side of 
the figure the hyal constrictor has been cut through near its lateral 
edge and turned forward. On the right-hand side it has been wholly 
removed, and the ceratohyal turned slightly forward. On both sides 
