HYDROCORALS OF THE NORTH PACIFIC — FISHER 531 



conspicuous dactylostyles. But the sides of tlie gastropore do not 

 converge so much toward bottom as in papillosa, while the broader 

 round-topped gastrostyle, as seen from above, is more than half as 

 broad as the gastropore proper (i. e., cyclosystem less dactylotomes). 

 In papillosa it is less than half. The gastrostyle shown in plate 54, 

 figure 5a, is average; some gastrostyles are lower and broader, while 

 a few approach more nearly the dimensions of plate 54, figure 4a 

 (papillosa). These are rather the exception and occupy smaller 

 gastropores, so that even here when seen from above the gastrostyle 

 is more than half the breadth of gastropore. 



A few male ampullae are visible on the fractured margin of type. 

 They are imbedded in the coenosteum, and the walls are very rough 

 from spicules. Two other fragments show female ampullae on the 

 fractured margin. They are a Httle larger than the male and their 

 height is a little greater than breadth (pi. 54, fig. 5a). 



The surface of the coenosteum is appreciably finer textured than 

 in papillosa, while the apparently characteristic papillae of that species 

 are here fewer and lower — certainly of no importance as a positive 

 character. A few dactylopores pierce the coenosteum but are not 

 on papillae as in calijornica. 



Color: The smallest colony is dull eosine pink, while the four larger 

 fragments are dull manganese violet. E. F. Ricketts, who collected 

 the specimens, states that larger colonies out of reach in the surf 

 appeared to be distinctly red, rather than purple. 



r?/^e.— U.S.N.M. no. 43272. 



Type locality. — Kyack Island, mouth of Sitka harbor, Alaska. 



Specimens examined. — Five small fragments collected by E. F. 

 Ricketts, of Monterey, Cahf., August 5, 1932. 



Remarks. — A. petrograpta forms reddish patches on hard rocks at 

 lowest tide level where it is exposed to surf. Mr. Ricketts states that 

 the habitat is the same as that of A. porphyra. While the colonies 

 vary in size, the larger are of the order of a foot in diameter and may 

 be partly exposed by receding tide. Specimens were very difficult 

 to procure on account of surf and the rugged nature of the shore. 



On the basis of available material, A. petrograpta is perfectly distinct 

 from A. papillosa. The latter appears to be related to A. californica, 

 while petrograpta is more like A. porphyra. A. porphyra differs radically 

 in having much larger cyclosystems with characteristically multiple 

 gastrostyles. But the form of the gastrostyle and the immersion of 

 each in a tightly enclosing chamber is not fundamentally different 

 from the structure of the single gastrostyle of petrograpta. Abnor- 

 mally petrograpta may have two gastrostyles to a cyclosystem, while 

 porphyra sometimes has only one. 



