Tir. TAt;i': sKoosiimm 



very closolv rolati'il to ('. hnroh.-s (i. ( >. SAUS — .,('. burfdlis. wlmli it \ci\' closcK- r('.s('ml)l('s". 

 The following; differences Ix'twccii these t\v<i forms arc noted m the work just mentioned: 

 .,C. tiiaxima is rather larijer and tlie sliell is not so densely retK iilated. 'I'lie outline of the sliell. 

 stHMi dorsally. is dilTereiit. and the spinides of the principal seta of the male atiteuiiule aic con- 

 siderably more ri)l)ust." 



0. 0. S.MiS writi's (1!MM». p. 1-Js) with repaid to ('. iiiii.riiiin: ..This form is verv closel\- 

 allied to . . . ('. Iiiifi'dlis. It is. howe\ci . of lai^ci' size, and di ITefs. moreovei'. in t he less st fondly 

 marked seiilpture of the shell, as also somew hat in the huin of the lattcf. ( )n a closer comparison, 

 some minor differences may also be found to exist in the struiture (d the several appendages." 



(J. W. MCl.l.KI! in his work of 11)01 put forward the view that the two forms are (juite 

 identical; the same view is also taken by this writer in his later works, lUOtia. p. Ill and 1!)12, 

 p. 87. This view has been adopted by P.T. Clf:ve, 1903 and V. VAm{.\, hmk;. Other writers 

 have, as we have seen above, accepted the species established hy (I. S. I')i; Ah^ and A. M. NOHMAN. 



Which of these opinions is the correct one? Are these two forms (piite identical or not? 



It seems to me impossible at present to answer this (piestion with complete certainty. 

 To do this it would be necessary to carry out renewed and careful investijrations on a considerably 

 more abundant material than that which was at my disposal. At present it seems to me most 

 probable that C. maxima is not cjuite identical with C. bnrealis. The differences between the 

 forms in question are, however, so small that it seemed to me to be best to ])ut the former as a 

 variety of the latter. 



The only rjuite certain difference I was able to find was that of size. Ct. O. Sahs states 

 that the male of C. maxima had a shell 3,20 mm. long and the female 3,50 mm. G. W. MOllrr's 

 males from Greenland measured 3,0 — 3,15 mm. The males of the maxima form investigated 

 by me had shells 2.95 — 3,2 mm. long; the females were 3,25 — 3,5 mm. long. The difference 

 between these figures and those previously given for ('. horealis is, of course, striking. 

 The maximum length for the latter species is (J = 2,35 (W \'A\i;a)^ 9 = 2,9 mm. May this 

 difference in size be connected with a difference in locality? Is the increase in size not merely 

 the result of a modification under Arctic conditions? This explanation, which may, of course. 

 seem a priori exceedingly probable, is very decidedly opposed, however, by the fact that I found 

 a typical mature C. horealis male as far north as lat. 79" 58' N.; the length of shell of this male 

 was not greater than that of the specimens from Lofoten; cf. p. 708 above. At lat. 76" 36' one 

 mature male and three mature females were found, all typical C. horealis; the male 

 measured, as is seen above, 2,3 mm., the females 2,4 — 2,7 mm., i. e. the latter were even some- 

 what smaller than the Lofoten specimens. It was these finds especiallv that caused me not 

 to follow G. W. MCller's example of uniting these two forms entirely. 



The posterior edge of the shell of the mature male is in most cases somewhat less rounded 

 in the maxima form than in the horealis form; cf. pi. XXXV, fig. 3, G. O. Sars, 1900 and my 

 appended fig. 1; there is, however, not cjuite complete constancy with regard to this character. 

 The shoulder vault of the shell is, in both males and females of the maxima, form, somewhat 

 less developed than in horealis. On account of this the shell, when seen from the side, gets 

 a straighter dorsal margin in the formei' form; see G. 0. Sar.s's figs., 1900 and (i. W. Mlller's 



