[373] INVERTEBRATE ANIMALS OF UINEYARD SOUND, ETC. Ce 
quarter of their length, beyond which they are separate and divergent. 
They are yellowish white, more or less spotted, especially toward the 
end, with orange, brownish, or blackish, which, in large specimens, forms 
streaks near the ends or even becomes confluent, making the tips very 
dark colored. The branchial orifice is surrounded by a circle of numer- 
ous bipinnate papille, which usually alternate with smaller and more 
simple ones ; the papillie of the dorsal tube are similar, but more simple. 
The Tagelus gibbus (Plate XX VI, fig. 181, animal; Plate XXX, fig. 
217, shell) is another inhabitant of muddy shores, which burrows deeply 
into the mud. This species is confined, on the shores, chiefly to the zone 
near low-water mark, but probably lives also in shallow water beyond 
the reach of the tides. In this species the foot is large and muscular, 
thick, tongue-shaped, and has a very wide range of motion, for the man- 
tle isopen along the whole length of the ventral edge of the shell. The 
tubes are separate, from the base, and are round, white, and capable of 
very great extension, for a specimen of ordinary size, kept in confine- 
ment, extended the tubes to the length of nine inches. These tubes 
are translucent, and at the end have small rounded lobes around the 
aperture, each lobe being furnished at its base, inside, with a small, 
orange, eye-like spot, which is probably an imperfect visual organ, and 
with two others on the inside lower down. The branchial tube has six 
of these lobes and ocelli; the dorsal one has eight. On each tube 
there is a row of small, white, slender, obtuse papille, corresponding 
to each terminal lobe, and running along the whole length of the tubes. 
The color of the animal is white throughout. This bivalve makes deep 
burrows in the tenacious mud, each of which has two orifices, not far 
apart, for the two tubes. By this peculiarity their burrows may be 
at once recognized, whenever seen. 
The Mulinia lateralis (Plate XX VI, fig. 185, B, animal) is occasionally 
found living at extreme low-water mark, on muddy flats, but its true 
home is on the soft muddy bottoms in shallow water, where t is often 
excessively abundant. In this species the foot is relatively large and 
muscular, more or less pointed at the end, and capable of assuming 
many different forms and positions; it has a wide sweep in its motions 
and ean be thrust forward or backward. The siphon-tubes are united 
nearly to the end, but the separation is indicated by a groove between 
them for nearly half the length. The branchial tube is the largest, and 
its orifice is surrounded by a circle of twelve to twenty-four, slender, 
elongated, simple papillie, each of which usually has a small, black, eye- 
like spot at its base ; a little below this terminal circle there is another, 
composed of smaller, very short, blant papille. The dorsal tube also has 
a subterminal circle of similar papillze, above which the tip forms a re- 
tractile cone, with the small, simple orifice at the tip. The animal is 
yellowish white, the tubes generally pale yellow. This species burrows 
just beneath the surface of the mud, and it is eaten in large numbers by 
the scup and other fishes. 
