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Proceedings of the Royal Society 
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tides strcemi, Sars., the cords are small, and lie within the hypoderm 
and strong circular coat in a line between the ventral longitudinal 
muscles. The slender oblique are attached on each side of the 
trunks, and must be carefully distinguished from the much larger 
muscles which cut off the great lateral longitudinal muscle 
externally. 
Sabellid^e. — In Sabella pavonina, Sav., the nerves occur in front 
as widely separated cords — each situated at the inner border of the 
ventral longitudinal muscle. A large neural canal lies above each. 
Externally are the circular muscular coat, the greatly thickened 
hypoderm and the cuticle. The feeble oblique muscles are partly 
inserted above the neural canal and partly into the basement- 
layer below and internal to the nerve. Proceeding backward, the 
neural canal increases very much in size, so that it occupies the 
whole area on each side of the central region, and presses the ovoid 
nerve-cord to the exterior. The canals appear to be filled with a 
slightly yellowish substance — consolidated in the preparations. The 
same relative position is maintained posteriorly, though the neural 
canal is smaller, and, as in front, placed superiorly. The arrange- 
ment in Dasychone bombyx , Dalyell, agrees in most respects with 
the foregoing. 
Chone and JEuchme seem to approach the next family in the 
arrangement of the nerve-cords and in the remarkable structure of 
the great longitudinal muscles. In Chone infundibvlum , Mont., 
the nerve-trunks occur between the ventral longitudinal muscles, 
and placed much more closely together than in Sabella. A large 
neural canal lies over each nerve. Externally are the strong 
circular coat, the thick hypoderm, and the cuticle. The oblique 
muscles are attached to the sides of the median vessel above the 
neural canals, and to the summit of the latter on each side. While 
the cords are lost in the ganglia, the neural canals remain distinct. 
In Euchone a similar condition exists, for though the cords are 
distinct anteriorly they are closely approximated posteriorly. 
Eriographidid^e. — In the anterior third of Myxicola infundi- 
bulum , Renier, the cords are approximated in the interval between 
the great longitudinal ventral muscles, and beneath the large 
blood-vessel. A neural canal appears to exist toward the superior 
border. The slender oblique muscles are inserted into the summit 
