536 MR JAMES RITCHIE 



just above the base, and monosiphonic, roughly pinnate ramuli, is typical. The 

 hydrothecae are free distally for rather less than half their length, the free portion 

 standing out from the stem almost at a right angle, and being marked on the upper 

 side by a few rather indistinct annular rugosities. 



Gonosome. — Not present. 



Locality, etc. — Depth, 100 fathoms. Off Gough Island. Lat., 40° 20' S. ; long., 

 9° 56' W. Date, 22nd April 1904. 



Sertularella tenella (Alder, 1857). 



Small specimens of this delicate colony some 7 mm. long have been found 

 growing on Synthecium robustum. They are quite typical in appearance, agreeing with 

 previous descriptions and figures. 



The following are average measurements : — 



Internodes. — Length from 0*55 to 0*8 mm. 



Hydrothecae. — Length, 0"5 mm. ; widest diameter, 0'25 mm. ; diameter at margin, 

 0'15 mm. 



Gonosome. — Not present. 



Locality, etc. — From offBurdwood Bank, lat. 54° 25' S., long. 57° 32' W., at a depth 

 of 56 fathoms. Date, 1st December 1903. 



Sertularella tricuspidata (Alder, 1856). 



A slender, pinnately branched colony 7 cm. high. It lacks the profuse branching 

 and matted appearance of a typical specimen of S. tricuspidata, but in other respects it 

 agrees closely with the specific description. 



Average Measurements. — Internodes : length, 0"75 mm. Hydrothecae : height, 

 0*6 mm.; portion adnate, 0'35 mm.; portion free, 0*4 mm.; diameter at margin, 0'3 mm. 



Gonosome. — Not present. 



Locality, etc. — From offBurdwood Bank, lat. 54° 25' S., long. 57° 32' W., at a depth 

 of 56 fathoms. Date, 1st December 1903. 



Sertularella rectitheca, n. sp. (PI. I. fig. 5.) 



A small, delicate colony some 9 mm. high, growing on the stem of Stauroiheca 

 reticulata. The stem is slender and unbranched, divided for some distance by slanting 

 nodes into short regular internodes 0"5 mm. long, and produced distally into a tubular 

 tendril-like process which was attached to a portion of the Staurotheca colony. The 

 internodes are much broadened half way up their length by a shoulder for the support of 

 the hydrothecae. These are alternate, cylindrical, about 0'5 mm. high by 0"15 mm. in 

 diameter, adnate up to the distal end of the internode in which they arise, then free for 

 the remaining third of their length. The hydrothecae are straight, the free portion 



