UNIVALVES——SERPULA. 193 
SERPULA.— WormM-SHELL. 
DESCRIPTION OF PLATE XXXIV. 
Div. I.—Fig. 4. S. contortuplicata. Dw. Il.—Fig. 2. S. anguina. 
Dy. I].—Fig. 1. S. lumbricalis. Drv. Il.—Fig. 5. S. retorta. 
Dy. I[].—Fig. 3. S. aquaria. 
Shell wnivalve, tubular, generally adhering to other substances. 
THE construction of the Serpule is extremely irre- 
gular, and the groups they form are no less diversified. 
They are invariably tubular, and sometimes present 
themselves detached, either straight or twisted, but 
more frequently in clusters spirally entwined, adher- 
ing to a variety of other substances. 
The colors of the Serpulz are generally nee pur- 
ple, yellow, tawny, pink, or white, and sometimes tinged 
with green. Of the species which are attached to extra- 
neous substances and form the first division, some are 
isolated and others collected into large masses, contain- 
ing many hundred spiral and twisted tubes, curiously 
interwoven: the shells of the former class have their 
whorls nearly contipuow, and resemble some of the 
Helices: such are the S. spirillum and_S. spirorbis. 
The S. vermicularis is an illustrative example of the 
aggregated species. 
The second division has also its isolated and aggre- 
gated species; to the former belong the S. protensa and 
S. lumbricalis, which is a flexuous shell, with a spiral 
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