BY W. M. BALE. 769 



ach other in front, separated behind, the outer side of each form- 

 ing a strongly salient angle below the aperture ; the body of the 

 hydrotheca projecting forward from the internode, the distal por- 

 tion twisted upwards; aperture nearly vertical, margin without 

 distinct teeth. 



Gonothecse rather small, ovate, with 5 or 6 strong transverse 

 costae ; one only on a shoot, springing from the basal part of the 

 proximal internode. 



This species, which I found running over the surface of a Flustra, 

 is very small, none of the shoots which I observed bearing more 

 than three pairs of hydrothscje, the peculiar twisted form of which 

 is very distinctive. The most nearly allied species is perhaps the 

 Dynamena confer ta of Kirchenpauer. 



SERTULARIA COMPLEXA, S. F. Clarke. 



(Plate XVIIL, figs. 1-4). 



Hydrorhiza stout, shoots simple, about half an inch in height, 

 with a pair of hydrothecse on each internode. Hydrothecae 

 opposite, in contact with each other in front, separated behind, 

 long, tubular, free for about J of their length, upper portion 

 curved outward, the hydrotheca-wall produced downwards into 

 two points below the inner side of the base ; aperture vertical, 

 margin with two lateral teeth or angular lobes, 



Gonothecse borne principally on the hydrorhiza, small, sub- 

 globular, truncate at the summit, with 6-8 distinct annulations ; 

 aperture operculate, margin not elevated, a few small irregular 

 teeth within the margin. 



Hab. Boncii Bay : Yucatan, America (Clarke). 



This slender species, which is found profusely over-running 

 leaves of Zostera or Cymodocea, very nearly resembles S. tuba in the 

 form of its hydrothecse, but differs from that species in its simple 

 habit and in the form of the gonothecse. The two spines which 

 in S. complexa project downwards from the base of the hydrotheca 

 into the cavity of the hydrocaulus are also distinctive, but are 



