52 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [346] 
mud. The presence of a large group of peculiar stout sete on each side 
of the fifth segment will distinguish this from all the preceding species. 
The young of this, like those of most of the annelids, swim free at the 
surface for some time, and are often taken in great numbers in the 
towing-nets. 
The Nerine agilis V., is still another representative of the group to 
which the last five species belong, and like them it has two long and 
large tentacles on its head, but it is a far more active and hardy species 
than any of them, and much better adapted for rapid burrowing. It 
accordingly lives on exposed beaches even where the sand is loose, and 
can also maintain itself on the exposed sandy beaches of the outer ocean- 
shores, exposed to the full force of the surf, its extremely quick burrow- 
ing affording it the means of protecting itself against the action of the 
sea. It lives in small round holes near low-water mark; unlike the 
related species, already mentioned, it has a very sharp conical head. 
The two large tentacles are about half an inch long, and originate close 
together on the upper side of the back of the head, and are usually re- 
curved over the back when the worm is swimming in the water, as it is 
capable of doing, but when it is wriggling about on the sand they are 
twisted about in all directions and variously coiled; aud when in their 
holes the tentacles are protruded from the opening. The eyes are four, 
small, black, placed close together in front of the base of the tentacles. 
The upper lobe of the lateral appendages is large and foliaceous and 
connected with the branchiz along the anterior part of the body, but 
partially free farther back. The body is two or three inches long and 
rather slender; the color is reddish or brownish anteriorly, greenish 
white on the sides, except on the anterior third; the branchia, 
which extend the whole length of the body, are light rel; tentacles 
greenish white. 
One of the largest and most beautiful Annelids of this region is 
the Diopatra cuprea, (Plate XIII, figs. 67 and 68.) This species grows 
to be more than a foot long, with the body depressed and often nearly 
half au inch broad. It constructs a very curious permanent tube in 
which it dwells very securely. The part of these tubes beneath the 
surface of the sand is composed of a tough parchment-like material, 
and often descends obliquely to the depth of two or three feet or more; 
the upper end of the tube projects two or three inches from the surface 
of the sand or mud, and is thickly covered with bits of eel-grass and 
sea-weeds, fragments of shells, and other similar things, all of which are 
firmly attached to the tube, but project externally in all directions, giv- 
ing this part of the tube a very rough and ragged appearance exter- 
nally, but it is very smooth within, and often it has an opening half an 
inch in diameter, or large enough so that the worm can turn around, 
end for end, inside of it. When undisturbed the occupant thrusts its 
head and the anterior part of the body out of the tube to the distance 
of several inches in search of food, or materials to add to its tube, ex- 
