308 MYXICOLA. 
statocysts. Branchie forming a half circle on each side, not caducous like those of 
Sabella, connected by a web almost to the tip, each filament with a webbed, flattened and 
tapering terminal process, sometimes enlarged at the base. No eyes. Body of two regions, 
round, somewhat fusiform, highly contractile. Ventral sulcus passes backward to the eighth 
segment cutting it obliquely as it goes to the right to end dorsally about the middle of the 
ninth. Anterior region of eight segments. first segment sends forward a short triangular 
process. Two segmental organs in the anterior region opening by a common duct on the 
dorsum. Bristles with finely tapered though rather short tips and narrow wings. They 
are both more slender and more minute posteriorly. Anterior region with rows of long 
crotchets. Posterior hooks forming a transverse series from the dorsal to the ventral surface, 
small, avicular, with a main fang and above it a comparatively large tooth. No ventral 
scutes or shields. Tube of mucus. The representatives extend to America (Verrill) and to 
the Antarctic Ocean. 
It is curious that no example of this genus was procured by the “Challenger,” its 
representatives perhaps being chiefly littoral or confined to comparatively shallow water. 
i 
CNN MELO al rained 
CK \ meal ih : 
S SN ‘| ‘ 
Fie. 162.—Transverse section of the body-wall of Myzicola infundibulum in the anterior region. 
In Myzxicola infundibulum, which Malmgren placed under the Eriographididee, the thin 
cuticle covers a hypoderm of considerable thickness which is directly fixed to the circular 
muscular layer surrounding the body beneath it and passing external to the nerve-cords. 
The dorsal longitudinal muscles are lappet-shaped, that is, narrowed on each side of the 
mid-dorsal line, which is occupied by the short mesentery supporting the alimentary canal, 
and enlarging in their progress to the lateral region. The ventral longitudinal muscles 
are of similar shape, and are separated in the middle line in the interganglionic areas by the 
small, rounded nerve-trunks above which is the large median (ventral) blood-vessel, which 
also lies between the upper edges of the ventral muscles. In transverse section both dorsal 
and ventral muscles are pennate. Anteriorly the wall of the alimentary canal is highly 
vascular, large blood-vessels being distributed on its surface. When a ganglion is cut the 
space between the ventral muscles is larger. Externally to the nerve-trunks is the circular 
muscular coat, the hypoderm and the cuticle, and a small neural canal is present superiorly 
in-each nerve-trunk. The slender oblique muscles appear to be attached over the nerve- 
trunks. The trunks fuse posteriorly, and have a single median neural canal superiorly. 
The close proximity of the large ventral blood-vessel to the nerve-trunks is noteworthy, 
