18 THE HYDROIDS. 



like opening in every respect like those of the pinna-bearing tube on which 

 there are 12 to 14 nematophores between each two adjoining pinnae. 



Gonosome : — Not present. 



Habitat : — Station 4630. Latitude N., 6 Q 52'. Longitude W., 81° 42.5'. 

 Depth, 556 fms. 



There are 6 tubes showing in surface view of the base of the main stem, 

 hence there must be at least 12 in it, and these apparently all come from 

 the hydrorhiza. Tbe hydrotheca-bearing tube disappears at the base under 

 some of the simple tubes. 



This species is nearest to C. dolkothcca Allman and C. flcxuosus Nutting, 

 but differs from them both in the compound character of the main stem, the 

 nodal joints of the pinnae, and in the structure and the arrangement of the 

 nematophores. Neither are there any "imperfect septa (septal ridges)" in 

 the parts of the stem at the backs of the hydrothecae. 



Plumularia helleri Hincks. 



Plate 15. 



Two colonies of this delicate Plumularian attached to a large spicule of a 

 siliceous sponge were collected in the Gulf of Panama; one at Station No. 

 4621 ; Lat. N. 6° 36', Long. W. 81° 44', depth 581 fms. ; and the other at 

 Station No. 4622, Lat. N. 6° 31', Long. W. 8P 44', depth 581 fms. 



A slight difference in the two specimens is noticed in the position of the 

 hydrothecae on the internodes: in the specimen from Station 4621 the inner 

 part of the rim of the hydrotheca is on a level with the node ; in the other 

 specimen the rim is below the node. 



Aglaophenia struthionid.es Murray 

 Plate 10, figs. 4.-6. 



A single stem of this beautiful species, with several corbulae, is from 

 Station 4643. Depth, 100 fms. ; bottom, broken shells and Globigerinae. 

 Locality about 4§ miles southwest by south from the west end of Hood 

 Island, Galapagos Archipelago. 



In several collections 1 have had from the Pacific Coast of the United 

 States, this has been the most abundant species. This extends the range of 

 Puget Sound to San Diego, southward to the Galapagos. It was described 

 by Murray in 1S60 as Plumularia struthionides, and by Clarke in 1870 as 

 Aglaophenia struthionides. 



