576 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
length grains of sand and mud become attached, and which form with 
this foreign matter a matted and tangled mass which covers not only 
the ventral region of the animal but extends up around and incloses 
the body, except the part of the dorsal surface which bears the si- 
phons. The body is thus more or less completely enveloped in a 
Text-flg. 3S. — Pandocia fibrosa (Stirupson). X 2.4. 
compact mass of mud and long tangled hairs, making it appear like a 
ball of mud of about double the size that it actually is. The test is 
exceedingly strong and tough. The largest specimens measure (when 
the above mentioned mass of mud and hair is removed) about 18 mm. 
long and somewhat less in the other diameters. 
Musculature of mantle well developed on nearly all parts of the 
body. The superficial layer consists mainly of a sheet of closely 
placed fibers which are not gathered into bands. The deeper layer 
consists of rather loose and irregular bands radiating from about 
the bases of the siphons. The mantle generally adheres firmly to the 
test. 
Tentacles numbering at least fifty or sixty, of various sizes arranged 
with little appearance of regularity, so that it is difficult to say how 
many orders are represented, but probably at least four. Very small 
tentacles, which, however, have the same tapering elongated form as 
the large ones, are present here and there in the intervals between the 
larger ones, but they are not very numerous. No atrial tentacles were 
observed. 
Dorsal lamina a plain-edged, rather narrow membrane. In pre- 
served specimens it will generally be found thrown into lateral undu- 
lations by the contraction of the tissues. The same is usually the 
case with the internal longitudinal vessels of the branchial sac. 
Dorsal tubercle conspicuous, C-shaped, horns neither inroUed nor 
