14 THE HYDROIDS. 
Thuiaria tubuliformis Marktanner-Turneretscher. 
Plate 9. 
There are about 20 colonies attached to pieces of a bivalve shell from 
Perico Island. The specimens are from 25 to 40 mm. in height, and several 
have gonangia. The internodes are described as “ bearing a branch and two 
hydrothecae on one side and a single hydrotheca on the other.” Some of the 
internodes in these specimens bear a branch and three hydrothecae on one 
side and two on the other. The tendency of the hydrothecae to arrange 
themselves in groups, mentioned by Nutting,’ and especially so toward the 
distal ends of the branches, is quite pronounced. The localities for this 
species hitherto reported are all from the Atlantic side of the continent, 
— Brazil, Florida, and the Bahama Banks. This is yet another instance 
of the same marine invertebrate occurring on both sides of the Isthmus of 
Panama. 
Sertularella tropica Hartlaub. 
Plate 10, Figs. 7-3, 3b. 
A few small, fragmentary specimens attached to a chitinous worm tube 
came from Station 4647, Latitude, South; 4° 33’, Longitude, West, 87° 42.5’. 
Depth, 2005 fms. Trawl, open net tow to surface from 800 fms. 
In Nutting’s table of the bathymetrical distribution of the Sertularidae, 
the greatest depth recorded is 1168 fms., and it is interesting to note that it 
is a record of this species, and in the Eastern Pacific not far from the Equa- 
tor. As the worm tube to which this specimen is attached is uninhabited, it 
may have been floating and have been picked up by the tow net on its way 
up from the 800 fm. line. 
This species was first named Sertularia variabilis by myself in 1894, an 
unfortunate christening, as that specific name was preoccupied. Hartlaub 
renamed it tropica in 1900, and changed it into the genus Sertularella. These 
two genera are not distinct enough to warrant a further complication of the 
synonymy by calling this again Sertularia. The determination of genera in 
the Hydroida is perhaps peculiarly unsatisfactory, inasmuch as there is often- 
times only the perisare from which the description is written, and in some 
cases only that of the trophosome. The recognition of genera being largely 
a matter of convenience, and as the fuller knowledge shows us ever more 
4 Special Bulletin, Smithsonian Institution, 1904, Part 2, p. 70. 
