LSTBROEDKA OF NORTH PACIFIC A\l> \n.i \< i.w WATERS FIBED 



The distinction is unfortunately 1 1 » » t bo simple. < Y I pedicellariae an 



mi the adambulacral apinee of all the specimens of miUleri < xamined l>y ma, and some- 

 times in fair cumbers. Thej are also abundanl mi the same spines of hyperb 

 The abactina] Bpinee do average larger on hypi and are often more uumerous 



than in Htiilltri. There is, however, a small but distinguishable difference in the 

 crossed pedicellariae. (PI. 8, iL r >. t. i". b; pi. 11, figs, l, l" Ic.) In hyperborea 1 1 1 * - 

 pedicellaria is wider (pi. 11, i'c_ r s. I, Ic) a- seen in profile, with a 1m t _r«r terminal lip 

 which is broader than in mnUeri. Tin' large specimen othyperborea from I < -« ■ Fjord, 

 Spitsbergen, has uumerous conspicuous spatulate Btraighl pedicellariae -i n til n r to 

 those of aretica. (l'l. 11, li<rs. i</, le.) This example has K 82 mm., and i- much 

 bigger than average specimens of mull,/:. 



Dr. A. Djakonov, of the Zoological Museum, Academy <>f Sciences, Leningrad, 

 made comparisons of specimens <>! /. mUlleri, L. hyperborea, and /. groenlandica at 

 my request and wrote me as follows: 



My Investigations have led n conclusion that: 1. Kalischewsky bad an incorrect idea 



of these Bpeoies and whal he held for /.. hyperborea was really /.. groenlandica in nil ■■.■!*•'- 2. /.. 

 gromlandica is a good Bpecies ami is clearly different from m Jtteri-hypeTborea. •'!. /.. hyperborea can 

 only with great difficulty be >i t I from mUlleri and i~. a- it seems, only its arctic form. I 



being intermediate specimens between them. 1. /.. to In- met with eastward of 



middle Murman coast of northern Russia; records of mUlleri from the coast of northern Siberia 

 arc referable to hyperburm. 



I think the relationship of aretica is with rat hor than with hyperb 



The crossed pedicellariae of aretica arc more like those of mtiHeri than of hyj»rborea, 

 and the genera] appearance of aretica, especially of forma beri is much like 



that of iimlltri. It is likely that the two specie- intergrade, probably through a 

 series of Blightly differentiated geographic forms. 



Yerrill (100!t. p. 553) has expressed the opinion thai hyperborea and aretica are 

 the same, hut in 191 I he recognized aretica as a full species without mentioning his 

 previous identification, nor pointing out the close similarity of the two. 



Aretica seems to be the equivalent of >/«//< • ■' in Bering Sea and the Arctic Ocean 

 to the north, ft differs from mxdleri in ha vine; either a closer, more capitate abactina] 

 spinulation or numerous spatulate straight pedicellariae or both in varying degrees. 

 The south Bering Sen form of aretica is larger than muUeri with heavier spines and 

 more uumerous pedicellariae of both sorts. 



I I P I \s II HI Vs in LOOKS, nc » Rpm-lM 



Plate 10, Figures 5 ll; Plate 17 Pigui 



Diag I lifft i ing from /.. aretica in ha\ in^ uniform, rather < lose-set . -lender, 



terete, often slightly tapered, striated but aoncapitate, hea\il\ sheathed abactina] 

 Bpinelets, the carina! series of which is not at all differentiated from the other Bpines. 

 The -peei,- occurs m a dwarfed form, .-exually mature at K l."i t « . 17 mm., in which 

 the skeleton and Bpinelets are relatively more delicate than in the large specimens, 

 and more delicate than in corresponding sizes ol /. aretica Type, K 39 mm., r 9 

 mm . R i 3 r; breadth of ray, just beyond base i-' to ll mm. Rays well arched 



with rounded sides and plane actinal surface, slender to medium stout, gently taper- 

 ing from it slightly swollen base to a blunt extremity. 



