THE STURGEONS AND STURGEON INDUSTRIES. 
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18. EXPLANATION OF THE PLATES. 
EXPLANATION OF REFERENCE LETTERS IN PLATES XXXVII TO LIX. 
J, Vent or anus; Au, Auditory capsule. 
jB, Barbels ; Bf, Branchial filaments ; BA, Bulbus arteriosus. 
Ch, Chorda or notochord ; Cop, Copul® ; CF, Cuvierian duct. 
De, Deutary ossification. 
-E, Eye ; BO, Exoccipital scute. 
B, Frontal scute; B, in fig. 51, membranous floor of aorta. 
GB, Gall-bladder ; GB, Genital folds or ridges ; G, Genital opening. 
H or Ht, Heart ; Eh, primary cerebral vesicle ; Hy, Hyoid ; HA, Hepatic artery ; EM, Hyomandibular 
bar. 
I, Inner coat of intestine in fig. 47 ; 1, I , I", intestine, and first and second loops of intestine ; i, ii, in, 
iv, V, branchial arches. 
II, F, X, Foramina for second, fifth, and tenth cranial nerves ; lA, Inferior arches of vertebr®. 
EpL, Embryonic, cephalic mesodermal tissue. 
LL', Right and left lobes of liver ; Ly, Lymph cord of spiral valve. 
M, Mouth ; M' and ME, Meckel’s cartilage ; M'" , Mesentery ; M"" , Bristle through opening in mesen- 
tery ; MD, Muller’s dirct or oviduct ; MCA, Anterior coraco-arcualis muscle. 
N, Kidney or Wolffian body ; also, nasal scute, fig. 45 ; Na, Nasal capsule. 
O, Outer coat of intestine ; OB, ffisophagus ; Or, Orbit ; Op, Opercle. 
P, Pancreas. 
PA, Abdominal pores ; PC', Transverse or pericardial septum ; PC, Pericardial cavity; PP, Pectoral 
fin ; Pf, Pf", Pre and post frontal scutes ; Pf, Pectoral fin, in fig. 18 ; PN, Pneumatic duct ; 
PV, Hepatic vessels ; PI and PQ, Palatopterygoid or palatoquadrate ; Py, Pylorus. 
R, Rostrum and rostral scutes; Rm, Adductor muscle of mandible. 
S, S', Spleen. 
Sp, Spiracle; Stf, Rostral disk; SV, SV, Spiral valve; ST, Stomach; Sy, Symplectic ; (SP, Spiral 
fold ; SO, Supra-occipital scute ; Sp, Neural spines. 
VG, Urogenital canals or ducts. 
F, Ventricle; F', Nerves going to barbels ; FV, Swim-bladder; FP, Ventral fins and their site in fig. 
52 ; FA', FA", FA'", Primary visceral arches in fig. 10. 
WG, Wolffian ducts in embryos figured. 
