HYDROCORALS OF THE NORTH PACIFIC — FISHER 545 



Of the species described by Pourtales from the West Indian region, 

 sulcata, Joliacea, cerpina, barbadensis, and contorta, the north Pacific 

 species shows resemblance only to D. sulcata (see pi. 74). In this 

 species the dactylotomes are on projections that on the distal parts of 

 branches approach the prominence of those of borealis, but when 

 specimens are compared the gastropores of borealis are quite evi- 

 dently at least 50 percent (sometimes 100 percent) wider than those 

 of sulcata and the marginal sulcus, mcluding the limiting dactylotome 

 projections, about twice as broad as that of sulcata. The ridges that 

 roughen the surface of the ampullae of sulcata are smaller, more 

 numerous, rounded, less porous, with a surface pohsh and without the 

 microscopic superficial spicules of borealis. 



