358 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
regards the operculum as little more than a toothed margin, the 
teeth coming together to form a covering. The form of the polyp, 
which according to Levin sen is of little moment, is quite similar 
in all four families, and the constancy of type should be recognized. 
The operculum on the other hand is an adaptive structure. 
21. Calicella syringa Linn. PI. 4, hors. 20, 20a, 20b, 20c. 
PI. 6, fig. 20 d. 
This form agrees perfectly with Hincks’s description. 
Diaphragm a simple shelf of dissimilar thickness, thickest at 
the outer extremity and running out to a very fine ledge under the 
hydranth. The basal chamber is part of the stem. 
Habitat. On stems of Tubular ia larynx, ITy dr allmania falcata, 
etc., at Port Townsend Bay. Also reported from Iceland (Hincks); 
Alaska (Clarke); East Spitzbergen (Marktanner-Turneretscher). 
Sertulariidae. 
It has been difficult to characterize this family, and to find a chief 
differential of value. Hincks’s early description is insufficient. It is : 
— “ Hydrothecae perfectly sessile, more or less inserted in the stem 
and branches; polypites wholly retractile with a single wreath of 
filiform tentacles round a conical proboscis; gonozooids always 
fixed.” Levinsen endeavored to improve upon this by finding a 
chief differential in the structure of the operculum. He says: — 
“ Forms with a well-developed segmented stem, whose bilaterally 
placed operculated hydrothecae are usually stemless, and frequently 
sunk into the stem or branches.” His diagnosis is based upon com¬ 
paratively few genera and species, and the nature of the operculum, 
its insertion, and the opposite-placed “ collar ” are points which 
necessitate a complete rearrangement of the old family Sertulariidae. 
Until these characters have been approved by further investigation 
and upon living material, and until the natural affinities are better 
understood than they are at present, it seems a better plan, in a work 
of the present kind, to adhere to the older system notwithstanding 
Allman’s objection to Gray’s division of the family. Schneider’s 
division of the family into a number of types is very convenient 
and probably represents as nearly as possible, considering our present 
knowdedge, the natural affinities of the groups. 
1. Sertularella group. The hydrothecae distinctly alternating, 
