ASTEROIDBA OF NORTH PACIFIC AND ADJACENT WATERS— FISHER 



63 



with magister, if it occurs at all, must take place between Icy Cape and southern 



Bering Sea. 



After examination of the type of typicus, Danielssen and Koren call attention to 

 the fact (1884, p. 37) that the original figures and description of the pedicellariae 

 given by Sars are not quite correct. They state that in the type the pedicellariae 

 are exactly like the figure given by Duncan and Sladen (1881, pi. 2, fig. 26). 



I have carefully examined pedicellariae of a specimen of typicus, believed to have 

 come from Norway, and find more numerous teeth on the shaft. The pedicellaria 

 figured by Duncan and Sladen is not in all probability a typical ventral one, as the 

 terminal teeth appear to be more like those of the dorsal pedicellariae, or of an inter- 

 grade between the two sorts. 



Although magister has much the same appearance as typicus the characters 

 offered by the very numerous major crossed pedicellariae are diagnostic, while the 

 extraordinary development of the actinal plates, in transverse series, is not found in 

 typicus, although undoubtedly latent there. As mentioned below, typicus may not 

 be even closely related to magister. 



The specimen from station 4243, Kasaan Bay, Prince of Wales Island, Alaska, 

 belongs quite evidently to the Alaskan rather than to the southern race of the species. 

 The major crossed pedicellariae are smaller than in megalabis, especially contrasting 

 with the Washington example of the latter, which, however, is not precisely typical. 

 The minor pedicellariae have the fewer proximal shank teeth of the northern form. 

 Some light is thrown upon the relationship of magister and typicus by two Ant- 

 arctic species, P. antarcticus Ludwig and P.jormatus Koehler, both of which appear 

 to be more closely related to magister than is typicus. 



P formatus Koehler (1920, p. 106, pi. 16, figs. 1, 9, 10; pi. 17, figs. 6, 7; pi. 58, 

 fi<r 4) from latitude 66° 8' S., longitude 94° 17' E., 120 fathoms, has a robust skeleton 

 and there are proximally four plates in each transverse actinal series; three further 

 alon<* the ray. R varies from 38 to 40 mm. The plates are stouter even than in P. 

 magister but the major crossed pedicellariae are closely similar in form although they 

 are somewhat larger in size (averaging 0.6 mm.) There are one or two teeth below 

 the terminal set of four. Koehler describes the straight pedicellariae (pi. 58, fig. 4fc) 

 as occuring in the ambulacral furrow. They are very rare in magister; occasionally a 

 small one °very similar to those of formatus, is found on the oral plates, less often at 

 wide intervals in the furrow. In fact they may be described as absent from the furrow, 

 since their presence there is so rare as to have little significance. 



P antarcticus Ludwig (1903, p. 35, pi. 4, figs. 32-38) from between 70 and 73 

 south and 82° and 87° west, 450 meters, has a skeleton which is much more delicate 

 and is analogous to that of megalabis. The major crossed pedicellariae are smaller 

 however (0 35 to 0.43 mm. high) and in form a little stouter than those of megalabis 

 especially as regards the three or four median teeth. The size of the pedicellariae 

 is nearer that of the major crossed pedicellariae of orientalis. The straight pedicellariae 

 of antarcticus are 0.16 to 0.22 mm. long, those of megalabis more than twice that and 



of a different form. _ , 



The presence in the Antarctic seas of two species so similar to three INortli 

 Pacific forms is of great interest, and is a bit of evidence in favor of the Antarctic origin 

 of the cold water of intermediate depths of the North Pacific. In time we shall 



