jg BULLETIN 76, imiTED STATES NATIONAL, MUSEUM. 



Even mnkin- liberal allowance for our meager knowledge of the region, it will 

 be evident that the coast of Asia north of Japan is much poorer m peculiar species 

 than the northwest coast of America, the former possessing four and the latter over 

 fifty characteristic forms. . , o • i 



It has been stated above that 76 per cent of the Phanerozoma and Spinulosa 

 are indigenous to the North Pacific. It remains to point out that of the intnisions 

 !•' per cent are derived from rircumpolar species, while about 12 per cent come 

 from the south, even as far as the extremity of South America, and that the shallow 

 water southern forms do not push so far north as the deeper water species. The 

 case with the circumpolar species is somewhat similar, for the forms which range the 

 farthest south are inhabitants of deep water. 



The derivation of the indigenous species, or rather of their ancestors, is too 

 clouded with uncertainty to admit of exact treatment. It may be suggested, how- 

 ever, without greatly overstepping the bounds of ascertained fact, that these forms 

 l)rob'ably came from the same sources as the species not pecuhar to the region, 

 namely, from the Arctic Ocean, from middle and South America, and to a shghter 

 extent from the direction of Japan. There remain, however, a number of forms 

 whose nearest relative outside the region can not be ascertained. 



SYSTEMATIC DISCUSSION OF THE FAUNA. 



Class ASTEROIDEA Burmeister. 



Free echinoderms with radially disposed gonads; with the ambulacral append- 

 ages, which are each connected with a double or single ampulla, confmed to an open 

 ventral ambulacral furrow and regularly arranged in two or four rows; radial 

 ambulacral water tubes and radial nerves exterior to ambidacral ossicles and not 

 covered by any plates; digestive system radiate and extending into the rays; respi- 

 ration by means of dermal gills or papulae; madreporic aperture abactinal; anal 

 aperture usually present. 



KEY TO THE ORDERS OF ASTEROIDEA. 



a'. Marginal plates usually large and conspicuous, defining the contour of body; abactinal skeleton in 

 the form of paxilliform plates," or flat, tessellate plates which are smooth or armed with granules or 

 spines, and either naked or covered with thin or thick membrane. Pedicellariae never peduncu- 

 late forcipiform, but spiniform, pectinate, valvate, or excavate. Papulse restricted to abactinal 

 area (except in some I.inckiidae and Asteropidse) circumscribed by the marginal plates. Mouth 

 plates prominent; ambulacral plates well spaced; tube feet in two series; rays usually 5 normally 



(except in some Luidia) Phanerozonia Sladen, p. 17. 



o'. Marginal plates not usually conspicuously large; abactinal skeleton not composed of true paxilliform 

 plates, nor in the form of a tessellated pavement, but usually more or less reticulate or imbricated. 

 PapuliE frequently but not invariably also intramarginal and actinal. Some form of abactinal 

 spinulation always present; tube feet with well-developed sucking disks. 

 b'. Actinostomial ring with adambulacral plates prominent; pedicellariae very rare, never peduncu- 

 late forcipiform nor excavate; ambulacral ossicles not crowded; abactinal skeleton composed 

 of thin, cloee-aet overlapping plates, or forming a more or less open reticulate network, either 

 regular or irregular; plates often cruciform with or without connecting independent essiclea. 



Spinulosa Perrier, p. 251. 



o The abactinal skeleton when paxilliform may be joined by definite and regular intermediate ossicles, 

 but is never irregularly reticulate; compare Solasteridae, which bear pseudopaxillK. 



