494 PROCEEDINGS OF THE NATIONAL MUSEUM VOL.84 



The region covered by this report includes all the water north of a 

 line drawn from the southern boundary of the United States (lat. 

 32° 30' N.) to the southern end of Sakhalin Island (lat. 46° N.). 

 All tropical and subtropical species are therefore extralimital. 



The material ^ upon which tliis paper is based is a part of the rich 

 collection of Stylasterina in the United States National Museum, 

 augmented by scattered specimens from other sources, cliiefly the 

 Hopkins Marine Station of Stanford University. The types of all the 

 new forms are in the collection of the National Museum. 



The following extralimital species have been figured: Crypiohelia 

 pudica Milne Edwards and Haime, plate 64, figure 1 ; Crypiohelia 

 japonica (Milne Edwards and Haime), plate 64, figures 2 to 4; Crypio- 

 helia giganiea, new species, plate 64, figure 5; Disiichopora sulcata 

 Pourtal^s, plate 74; Disiichopora gracilis Dana, plate 75. 



Systematics of the Stylasterina present difficulties peculiar to the 

 gi'oup in addition to those apparently inherent in the Coelenterata. 

 Material for the most part consists of the dried skeleton of the colony, 

 frequently imperfect. There is a slight sexual dimorphism added to 

 the pitfalls presented by variation due to environment and lineage. 

 Even in alcoholic material the gastrozooids and dactylozooids are 

 often invisible by retraction, while the contents of the ampullae have 

 proved to be of no practical value in difTercntiating species. Finally, 

 the structures available are all very small and must be studied and 

 drawn under high magnification, illuminated by a beam of concen- 

 trated light. It scarcely needs pointing out that great care must be 

 exercised in taking accurate measurements. Under these conditions 

 the comparison of elements and evaluation of variations imposes a 

 severe strain upon any but the strongest eyes. Such painstaking 

 analysis is necessary before progress can be made in the natural 

 history of this group. The papers of H, N. Moseley and Dr. Hjalmar 

 Broch have set a standard of excellence that unfortunately only a few 

 have tried seriously to equal. Much of the literature is vague and 

 sketchy judged by modern standards and can not be relied upon in a 

 critical study. 



The north Pacific is far richer in indigenous species than the north 

 Atlantic. Siylasier gemmascens alaskanus and Allopora norvegica 

 pacijica are representative forms of two well-known Atlantic species. 



1 My thanks are due to the authorities of the U. S. National Museum for the privilege of studying its 

 collections; to those of the Peabody Museum, New Haven, Conn., and the Museum of Comparative Zoology, 

 Cambridge, Mass.. for the loan of material for comparison; to Dr. Sixten Bock, of the Riksmuseum, Stock- 

 holm, for the loan of north Atlantic material and of literature; to Dr. Hjalmar Broch, of the Royal Frederick's 

 Unlver.sity, Oslo, for the identification of Japanese and Okhotsk Sea material and for the loan of examples of 

 several of his species; to Dr. T. Wayland Vaughan for material, chiefly Distichopora; to Dr. H. Hattori, 

 Biological Laboratory, Imperial Palace, Tokyo, Japan, for the gift of a representative collection of Japanese 

 Stylasterina; to Dr. Elisabeth Deichmann, Museum of Comparative Zoology, for aid in various ways; 

 to Prof. G. E. MacOlnitle for several photographs of specimens: and to E. F. Ricketts, of Monterey, Calif., 

 for the types of Allopora pelrograpla. 



