262 University of California Publications. [ ZOOLOGY 
well developed zocecia there are three spines on the outer mar- 
gin, the lower of these frequently bifid, the second often quite 
long, and the third, or uppermost one shorter and sometimes 
missing; two spines on the inner margin, the lower generally 
bifid, the upper frequently lacking or broken. Lateral avicularia 
of moderate size, usually found on each zoccium. A series of 
sessile, frontal avicularia (f7. av.) extends between the zocecia, 
each avicularium situated usually at the base of the spine on 
the inner margin nearest the scutum. These frequently stand 
out prominently, the beak opening upward, so that the zoccia 
frequently have the appearance of being flanked on each side 
by an avicularium, the one on the inner side being slightly 
smaller than that on the outer. The zocecium at the bifureation 
of a branch usually bears a raised avicularium of extraordinary 
size, with elongated beak directed obliquely, sometimes to the 
right, sometimes to the left (67. av.). Vibracular chamber dorsal, 
large, its length equalling half that of the zocecium on which it 
is placed (fig. 42, v. ch.) ; vibraculum long, two and a half times 
as long as the individual zowcia (fig. 41, v.). The rootlet arises 
from near the base of the vibracular chamber, toward the outer 
side (figs. 42 and 43, r.) The rootlets are developed only on 
the lower zocecia of a colony; in the upper zoccia the place of 
the rootlet is marked by a pore (fig. 42, p.) Oacia numerous, 
large, reaching to the margin of the aperture of the zocecium 
next above, and sometimes covering it (fig. 41, oe.) ; somewhat 
flattened and marked by numerous pores. 
This species grows in large bunches, and being very calear- 
eous, and having many long vibracula, spines and other appen- 
dages which catch and hold debris, it is remarkably coarse and 
dirty in appearance and rough to the touch. It strongly re- 
sembles Caberea, and the vibracular cells while not as large as 
those of that genus, yet show affinities to them in size, and in 
the length and slope of the groove. This species likewise shows 
certain resemblances to S. cervicornis, Busk (752), but its habit 
is very different and it does not possess the peculiar scutum for 
which the latter is named. 
S. diegensis is extremely abundant at San Diego on the rocks 
at Ballast Point, on floats at Coronado, and wherever it can get 
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