HYDROCORALS OF THE NORTH PACIFIC — FISHER 543 



Genus DISTICHOPORA Lamarck 



Distichopora Lamarck, Histoire des animaux sans vertebres, vol. 2, p. 198, 1816 

 (type: Madrepora violacea Pallas). 



DISTICHOPORA BOREALIS, new species 



Plate 70, Figure 3; Plate 71; Plate 72; Plate 73 



Diagnosis. — Resembling D. sulcata Pourtales but differing in having 

 the marginal sulcus about twice as broad, larger gastropores, still 

 more prominent dactylopore projections, and much more strongly 

 corrugated ampullae; surface of coenosteum minutely spiculated 

 rather than uneven and glossy. 



Description. — The colony branches mostly in one plane after the 

 habit of typical Distichopora, but the branches are sometimes twisted 

 or bent. At the base of the fragment from station 4781 (pi. 71, fig. 4) 

 two of the main stems anastomose, and the neat flabellate structure 

 is interrupted in the manner shown by the photograph. 



The gastropores lie close together in a well-defined sulcus, the raised, 

 rough borders of which are occupied by a series of tilted, slitlike 

 dactylopores (or dactylotomes) oriented transversely or obhque- 

 transversely to long axis of branch. Each dactylopore forms the 

 aperture of a gouge-shaped projecting hp, as in Errinopora, these 

 projections becoming more and more prominent on the distal portion 

 of branchlets. Here the margins of branclilets in profile are strongly 

 dentate on account of the dactylopore processes (pis. 72, 73). 



The dactylotomes are about half as long as width of gastropore 

 (varying one-third to two-thirds). Gastropores (from 0.25 to 0.425 

 mm in width) are spaced usually one-half to their own diameter apart. 

 The spacing of dactylotomes is irregular, but there is frequently one 

 on either side opposite a septum between two gastropores; and one, 

 or occasionally two, on either side, corresponding to the gastropore. 

 There are no dactylostyles. 



The gastropores are very deep, slightly curved, and descend at a 

 sharp angle to long axis of branch. Most of them end at center of 

 branch, being separated from the series of opposite side only by a thin 

 septum. The walls are beset by crowded short irregular spicules. 

 The gastrostyle is very slender, usually long, and bristling with obhque 

 sharp delicate spicules. The tip may be seen in a cleaned specimen by 

 looldng into the gastropore on the axis of its slant. Of sporadic oc- 

 currence on the front and back of larger stems are primitive cyclo- 

 systems consisting of a gastropore (sometimes 2 or 3 of unequal size) 

 surrounded by upward of 10 dactylopore projections, with the dactylo- 

 tomes turned toward the gastropore. These are usually on a slight 

 convexity and are the first appearance of new branchlets. A similar 

 structure is found on some specimens of D. violacea forma coccinea 

 (U.S.N.M. no. 8978, Tahiti). 



