174 



DEPARTMENT OF THE NAVAL SERVICE 



Serhdaria cornicina (McCrady). 



Trophosoine. Stem unbranclied, divided into regu- 

 lar internodes, each of which bears a pair of hydro- 

 thecse., which are iu contact for about two-thirds of 

 their length and then turned abruptly outward; mar- 

 gin with two teeth and a two-parted operculum. 



Gonosome. Gonangia oval, with distinct, short 

 collar; surface regularly annulated. 



No. 9'0. 

 SertiiligHa cornicina. 



Serfularia pumila Linnaeus. 



Trophosoine. Stem uubranched or with opposite 

 branches; a pair of hydrothecae to each internode, tubu- 

 lar, free from each other, curved outward, the distal 

 half free; margin with two teeth. 



Gonosome. Gonangium obovate, with a narrow 

 collar and wide apertvire.* 



Genus Thuiaria. 



No. 91. 

 Seriularia pumila. 



Trophosoine. Hydrothecae in two rows on stem and branches; hydrotheose with 

 not more than two teeth; operculum of one abcauline flap or two flaps. 



KEY TO SPECIES. 



a Branches only on two sides of the stem. 



h Stem long and slender, primary branches much branched. 2\ cupressina. 

 hh Stems shorter and more rigid; branches relatively longer. 



c Hydrothecae suib-opposite. T. similis. 



cc Hydrothecae strictly alternate. 

 d Branches stout and rigid. 

 dd Branches slender. 

 aa Branches on all sides of the stem. 



e Distal branches forming a dense tuft. 

 / Hydrothecae sub-opposite. 

 // Hydrothecae definitely alternate. 



g Primary branches branched dichotomously, all branches short and 



T. lonchitis. 

 T. latiusculu. 



T. fahricii. 



stiff. 

 gg Branches long and less rigid. 

 ee Branches on the distal portion of the stem loosely arranged. 

 h Hydrothecae almost wholly immersed. 

 hh Hydrothecae less than haK free. 

 hhh Hydrothecae more than half free. 



Thuiaria argentea (Linnaeus). 



Trophosome. Colonies often growing in clusters, 

 stem slender; branches rise from all sides of the stem 

 but irregularly, these branch dichotomously; hydro- 

 thecae usually definitely alternate but occasionally sub- 

 opposite, rather distant, curved gradually outward, 

 nearly one-third free; margin with two teeth, one often 

 larger than the other; operculimti with two flaps. 



Gonosome. Gonangia long-obovate, usually with 

 two shoulder spines; collar short. 



T. thuja. 

 T. rohusta. 



T. immersa. 



T. argentea. 



T. tenera. 



No. 92. 

 Thuiaria argentea. 



