Gill Arches of Teleostean Fishes — Nelson 
395 
Figs. 1-6. 1 , Conger marginatus, gill arch skeleton, ventral view. Bl-4, basibranchials ; Hl-3, hypobran- 
chials; Cl-5, ceratobranchials ; LP, lower pharyngeal dermal tooth plates. Cartilage stippled. Articular carti- 
lages at distal tips of ceratobranchials not shown. 2, Conger marginatus, dorsal view. El-4, epibranchials ; 
1,2-3 , ( infra )pharygobranchials; UP3-4, upper pharyngeal dermal tooth plates. Articular cartilages at distal 
tips of epibranchials not shown. 3 and 4, Gorgasia sp. 3 and 6, Ariosoma bowersi. 
In Mystriophis and Brachysomophis (Fig. 9) 
C4 has lost its double articulation with B4, 
but C5 is prominent. C4, however, is without 
any direct articulation with B4, being supported 
entirely by C5, which retains a firm articulation 
with B4. From this condition may have been 
derived that of Myrichthys (Fig. 8) and 
Ophichthus (Fig. 10). Cirrhimuraena and 
Myrichthys are alike in having the proximal 
portion of C5 cartilaginous, situated between 
C4 and B4, the distal portion extending pos- 
teriorly as a thin filament of cartilage {Cir- 
rhimuraena) or bone (Myrichthys ) . In Lethar- 
cus, C5 is present proximally as a small cartilage 
between C4 and B4, but seems entirely absent 
distally. Reduction of C5 has proceeded some- 
what differently in Ophichthus (Fig. 10). C4 
is without a proximal articular cartilage, being 
supported entirely by the lower pharyngeal 
tooth plates, which it seems have surrounded 
and fused with C5, leaving only the inter- 
mediate cartilaginous portion of C5 as evidence 
of the fact. 
The only other ophichthine examined having 
an ossified C5 is Caecula (Figs. 11, 20). In 
this form C4 has retained its primitive connec- 
tion with B4, but not a double articulation as 
in Bascanichthys. 
Gill arch structure in Phyllo phichthus, Calle- 
chelys, and Machaerenchelys is about that shown 
for Leiuranus (Figs. 17, 18). C5 is lost al- 
together, perhaps fused with the tooth plate or 
with C4. 
Relationships between the genera examined 
here have never been established. Gill arch 
structures, however, suggest certain relation- 
ships. One lineage may perhaps be represented 
by those forms having C4 not articulating with 
B4, but being supported by C5, including 
Mystriophis— Brachysomophis— Ophichthus, with 
Myrichthys, Cirrhimuraea—Letharchus branch- 
Figs. 7—10, 1 , Bascanichthys teres, porterior por- 
tion of gill arch skeleton, ventral view. Ventral articu- 
lation of C4 with B4 not shown on right side, where 
a portion of cartilage is omitted to show dorsal ar- 
ticulation. 8, Myrichthys maculosus. 9, Brachyso- 
mophis henshawi. 10, Ophichthus polyophthalmus. 
