DESMOSCYPHUS. • 25 



the specimens are immature, and would have acquired a greater develop- 

 ment in their adult state, it is a much smaller form than S. pmnila. Fur- 

 ther, in S. pumila the opposed sides of the hydrotheca3 composing each 

 pair converge from above downwards, while in S. exigua they are parallel. 



Sertularia distans. 

 PL XVI. Figs. 9, 10. 

 Trophosome. — Hydrocaulus attaining a height of about an inch, simple 

 or with an occasional branch ; internodes rather long and prolonged by an 

 attenuated extension below each pair of hydrotheca^. Hydrothecaj tubular, 

 with the distal half free and divergent, and the opposed sides of the proxi- 

 mal halves parallel. 

 Gonosome not known. 



Dredged off Tennessee Reef from a depth of 21 fathoms. 



This species bears considerable resemblance to ^S*. inanila, from which, 

 however, it differs in the much greater length of its internodes and con- 

 sequent distance of its pairs of hydrothecfe. The orifice of the hydrotheca 

 is cut off' obliquely above and below, so as to present two broad lateral 

 teeth, and the intervals between these are closed by two thin membra- 

 nous valves. Each of these valves is composed of delicate superimposed 

 lamina?, which may be usually seen partially separated from one another, as 

 thin exfoliating films. 



The species resembles also S. gracilis Hassall in the length of its inter- 

 nodes, but it is a larger form. 



In the absence of gonosome it is imj)ossible to approximate it closer 

 to any European form. 



" DESMOSCYPHUS Allman nov. gen. 



Generic Character. Trophosome. — Hydrocaulus jointed, each internode 

 corresponding to one or more pairs of hydrothecfe. Hydrothecfe adnate to 

 one another in pairs, each pair adnate to the side of the hydrocaulus. 



Gonosome. — Gonangia simple, borne along the front of the hydrocaulus. 



The genus Desmoscyphus was originally constituted for a hydroid from 

 the New Zealand shores.* It resembles most of the species of Thuiaria in 

 the extent to which the hydrothecse are adnate to the hydrocaulus, but it 



* Allman on New (Jenera and Species of Hydroida, Journ. Linn. Soc. Zoology, Vol. XII. 

 4 



