CALKINS: SOME HYDROIDS FROM PUGET SOUND. 
359 
with a more or less distinct joint between each two. Mouth of the 
hydrotheca toothed, operculum of many parts (all of Hincks’s Ser- 
tularellas; also those of Allman and Bale). 
2. Dynamena group. The hydrothecae opposite, a joint 
between each pair ; side branches, when present, arising from one or 
from both components of the pair of hydranths; mouth of hydro- 
theca generally Avith two teeth ; operculum simple. To this group 
belong Hincks’s Diphasia rosacea and D. attenuata / I), fallax 
Johnston ; D. pinaster Ellis & Sol.; Pallas’s D. lamarisca and D. 
pinnata ; Hassall’s Sertularia pumilci and S. gracilis / S. opercu- 
lata Hincks; S. hi spin osa Gray; S. minima Thompson ; S. 
m a c r o ca rp a Bale. 
3. Thujaria group. Hydrotheca more or less alternating, 
often almost opposite, closely placed and many to an internode. 
Side branches invariably arising from a singly-placed hydranth. 
Mouth of the theca generally smooth, operculum simple. Here 
belong Hincks’s Diphasia alata ; Ellis and Solander’s Sertularia 
filicula , S. abietina , S. argentea / Sertularia cupressina Hincks ; 
Thujaria thuja Hincks; T. lonchitis Hincks; Sertularia diffusa 
Allman; S. elongata , S. tenera Sars; S. maplestonei Bale; S. 
huttoni , Diphasia mutulata Busk; and Dynamena tubuliformis 
Marktanner-Turneretscher. 
4. Pasythea group. Hydrothecae. opposite ; a variable number 
of pairs closely packed upon the middle portion of an internode. 
Here belong a feAv easily recognized forms, e. g., P. denticulaia 
Ellis and Solander. 
5. Selaginopsis group. Hydrothecae arranged in more than 
two rows, closely packed together in great numbers on an inter¬ 
node. Selaginopsis cylindrica Clarke and S.fusca Johnston. 
6. Hydrallmania group. Hydrothecae on side branches dis¬ 
tinctly in one row, many packed together upon an internode. TI. 
falcata Linn. 
1. Sertularella group. 
22. Sertularella conica Allman. PI. 4, figs. 22, 22a, 22b. 
Hydrocaulus attaining a height of about an inch and a half, simple 
or with an occasional branch. Hydrothecae springing from points 
close to the distal ends of the internodes; they are tumid towards 
the base and narrowed towards the orifice and slightly marked with 
corrugations on the upper side. 
