200 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 4 



Hydractinia prolifica, new species 

 Plate 22, Fig. 1 



Trophosome. — Colony covers closely a large gastropod shell. Nutri- 

 tive zooids are placed close together around the margin, but they are 

 pretty well crowded out of the portion of the shell farthest from the 

 margin. The individual zooids have great power of extension even for 

 Hydractinia, the longest observed being 4 mm. The tentacles are fewer 

 than usual, 12-15. 



Spines. — The spines are long, up to 0.75 mm, and very numerous; 

 usually smooth, but sometimes rough or even spiny on the margin. 



Gonosome. — (Only male colony observed.) The generative zooids 

 are crowded on the more protected portion of the shell; they are small, 

 about 1.0 mm in length, without tentacles. The gonophores are large for 

 the size of the hydrocaulus, scattered but relatively close together, as 

 many as 6 of them, on the one zooid. 



Other Zooids. — No sensory or defensive zooids could be distinguished 

 in the preserved specimens. 



Distribution. — Station 944-39, 10 miles SW of Secas Islands, Pana- 

 ma, 30 fathoms. 



Remarks. — This species resembles H. echinata (Fleming) more than 

 any of the species so far reported from the Pacific coast, but the gono- 

 phores are more numerous, the spines longer, more slender, with less 

 tendency to form secondary spines, and much more numerous. If the 

 distribution range of H. echinata were more propitious it might seem 

 possible that H .■ prolifica was derived from that species. 



Family PennaHdae 



Genus PENNARIA 

 Pennaria tiarella (Ay res) 

 Globiceps tiarella Ayres, Proc. Boston Soc. Nat. Hist., 1854, p. 193. 

 Pennaria tiarella McCrady, Gymno. Charleston Har., 1859, p. 153. 



Fraser, Hancock Hyd., 1, 1938, p. 25. 

 Fraser, ibid., 3, 1938, p. 132. 



Distribution. — San Pedro, Calif.; San Francisco Bay, east of Panama 

 City, shore; off La Libertad, Ecuador, 10 fathoms. 



