142 PEOr. ALLMAN ON NEW HTDEOIDA FEOM 



half their height, then diverging at a yery wide angle, and ter- 

 minating in a deeply-cleft orifice ; pairs of hydrothecse distant ; 

 hydrothecae of each pair closely approximate on the pinnae, more 

 widely separate on the stem. 



Gonosome not known. 



Locality. Atlantic, attached to floating gulf-weed. 



Serttilaria amplectens attains a height of about half an inch. 

 It is a very delicate form, rendered remarkable by the close 

 approximation of the hydrothecse in each pair on the pinnately 

 disposed branches. The stems from which the pinnae arise also 

 carry hydrothecae, but these are here subopposite and less closely 

 approximate, while the joints of the stem are few in number 

 and are situated at uncertain intervals. 



Yiewed laterally, the approximation of the hydrothecae, back 

 to back, or by their epicauline sides, resembles the characteristic 

 condition of the hydrothecae in the genus Desmoscyphus. In the 

 present species, however, this approximation is the result of the 

 extent to which the internode is embraced by the hydrothecae, 

 and instead of being, as in Desmoscyphus, confined to one side of 

 the internode, it is equally present on both. 



ISTo trace of gonangia can be detected, and the frequent ab- 

 sence of gonosome in sucli Sertularians as are found on floating 

 forms of Sargassum and its usual presence in such as inhabit 

 rooted forms, is, as Miss Gatty has remarked to me, a fact worth 

 noting in connection with the absence of a reproductive system 

 in the floating seaweed and its presence in the rooted one. 



Seetulaeia megalocaepa, n. sp. (PI. XVI. figs. 5-7.) 



Trophosome. — Stems simple, attaining a height of about y\,- of 

 an inch, springing at short intervals by a spirally twisted proxi- 

 mal extremity, which is destitute of hydrothecae, from a creeping 

 stolon, which is also spirally twisted ; internodes separated from 

 one another by a deep constriction. Hydrothecae exactly oppo 

 site, tubular, adnate to the internode for somewhat more than 

 two thirds of their height, and then becoming free and divergent ; 

 orifice with its apocauline margin cleft so as to form two acute teeth. 



Gonosome. — Gronangia very large, nearly globular, destitute of 

 annulation, springing by a well-defined peduncle from the side 

 of the proximal hydrotheca-bearing internode just below the 

 base of the hydrothecae, and opening by a terminal orifice, which 

 is supported by a very short cylindrical neck. 



Locality. Australia? 



