INVERTEBRATE ANIMALS OF VINEYARD SOUND, ETC. 373 



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 papilla?, which usually alternate with smaller and more 

 simple ones ; the papilke of the dorsal tube are similar, but more simple* 



The Tagelus gibbus (Plate XXVI, 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 is open 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 papillae, 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 XXVI, fig. 185, e, animal) is occasionally 

 found living at extreme low-water mark, on muddy fiats, 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 can 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 papilke, 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, blunt papillae. The dorsal tube alsohas 

 a subterminal circle of similar papilla?, 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. 



