114 UNITED STATES NATIONAL IVIUSEUM BULLETIN 251 



mm. X 19 mm. in extent and 9 mm. in thickness, is encrusted ex- 

 ceptionally densely with sand grains. 



Test somewhat hard, gelatinous, translucent, contains in thoracic 

 layer many small, oval pigment masses, bluish, purplish black, or dark 

 olive. Pigment masses may be scattered throughout entire colony in 

 some specimens, but usually are very scarce in abdominal and bottom 

 layers. In thoracic layer, in addition to pigment masses, are many 

 whitish masses of shape and size the same as pigment masses, but con- 

 taining no pigments. Abdominal and bottom layers and peripheral 

 part of colony contain various amounts of minute sand grains, also 

 some fecal pellets embedded in the bottom layer. Sand grains very 

 sparce or quite absent in thoracic layer. Amount of pigments, sand 

 grains, and fecal pellets embedded in test varies according to colony. 

 In some specimens the thin superficial transparent layer is defined 

 clearly and minute, up to 38/x, in diameter, round or oval and milky 

 white structureless bodies, probably secretion products, are scattered 

 on the surface. Zooids at least 4 imu. in length in a strongly contracted 

 state, but may reach 9 mm. in a somewhat extended condition. Thorax 

 occupies a third to about half of entire body length, but may be only a 

 third of the abdomen's length when strongly contracted. Color yel- 

 lowish orange or reddish brown, probably reddish orange in living 

 animal. No system found in arrangement of zooids. Both apertures 

 6-lobed, atrial siphon comparatively long. Longitudinal and trans- 

 verse musculatures well developed on thorax. On each side 10 to 30 

 longitudinal, 25 to 60 transverse muscles, the latter confined to stig- 

 matal area of thorax, and nm beneath former. In some zooids ex- 

 amined, most of about 60 transverse muscles unite on dorsal side into 

 approximately 35 bundles ; about 10 posterior ones nm obliquely. Sev- 

 eral dorsal longitudinal muscles very fine. Posterior part of thorax 

 and anterior part of abdomen sometimes swollen by strong contraction 

 of longtiudinal muscles. A fairly strong but very short retractile 

 muscle may be f omid at posteroventral corner of thorax in some zooids. 

 From 12 to about 20 stigmata in each of three rows; two or three dorsal 

 ones of first row arranged along dorsomedian line as shown in fig. 39<?. 

 Tentacles 12-16, also some minute ones ; generally larger and smaller 

 ones alternate regularly. Ciliated groove a small oval opening. 

 Dorsal languets slightly displaced to the left side from dorsomedian 

 line. Peripharyngeal band, both sides of anterior part of endostyle 

 and transverse vessels may be purjjlish brown in some cases. Yellow- 

 ish or purplish-brown pigments may also be found deposited between 

 stigmata. Two pairs of longitudinal muscle bands run along abdomen 

 and end on right side near posterior end of abdomen. Mantle is some- 

 times reddish brown. Stomach situated at level of posterior one- 

 fourth of abdomen and smoothly surfaced. Hind stomach and mid- 

 intestine distinct ; proximal end of rectum markedly constricted from 



