26 DESMOSCYPHUS LONGITHECA. 
“= 
differs from this genus in the fact that the hydrothece are also adnate 
to one another in pairs, and thus brought all to one side of the hydro- 
caulus; while a still further difference is found in the fact that the inter- 
nodes may in some cases carry each a single pair of hydrothece, as in Ser- 
tularia. : 
In the New Zealand species, Desmosceyphus Buskii, the main stem is divided 
into mternodes of variable length, carrying each a variable number of pairs 
of hydrothecs, while the branches are regularly divided into equal internodes 
each with one pair of hydrothecz. In the species here described from the 
Gulf Stream (D. longitheca), the entire hydrocaulus is regularly divided into 
internodes, each carrying a single pair of hydrothece. 
Desmoscyphus longitheca. 
Pl. XIV. Figs. 3-6. 
Trophosome. — Hydrocaulus attaining a height of about an inch, pinnately 
branched ; pinne alternate, much contracted at their origin; main stem and 
pinne divided into regular internodes, each internode carrying a single pair 
of hydrothece. Hydrothece long, tubular, with semicircular orifice, which 
is closed by a valve-like lid; along the branches and the greater part of 
the main stem adnate to one another in pairs for nearly their entire height, 
but becoming free and diverging from one another close to their distal ends; 
towards the basal end of the stem the hydrothecw of each pair receding 
from one another and ultimately disposed on two diametrically opposite 
sides of the internode. 
Gonosome not known. 
Key West, shallow water. 
Desmoscyphus longitheca constitutes an interesting transition form by which 
the genus Desmoscyphus becomes connected with Sertularia. For while in 
D. Buskii the branches alone are divided into equal internodes, each carry- 
ing a single pair of hydrothec, the main stem being composed of internodes 
of variable length, each with a variable number of hydrothecsx, in the present 
species both stem and branches possess the Sertularian character of division 
into equal internodes, with a single pair of hydrothecs: upon each. 
Further, in D. longitheca the hydrothece composing each pair, where they 
approach the base of the main stem, begin to recede from one another, the 
separation gradually increasing, until just above the hydrorhiza they are 
situated upon opposite sides of their supporting internode exactly as in a 
