I916. No. lO. THE LOWER CAMBRIAN HOLMIA FAUNA. Ill 



the South Norwegian mainland, had probably a ver\- much more consider- 

 able extent both in a southerly and north- westerly direction than can be 

 directly proved, and it must have acted as a faunistic barrier with relation 

 to the western faunae. At that time, theretbre an independent development 

 of form could take place in the Fennoskandian sea, and particuiarl}- in the 

 case of Mesonacidae this resulted in the development of remarkable genera, 

 {Holmia and Kjenilfia, and also probably Schmidtiellus.) 



We cannot therefore assume, that the series of Central Norwav have 

 a lost faunistic interval, which according to Walcott corresponds to the 

 uppermost part of the Lower Cambrian. As evolved in an earlier section, we 

 have an even transition in the series, from the Holmia Kjendfi zone to the 

 Paradoxides Ølandicus zone. Between these, we have first the zone con- 

 taining Strcimclla Lifuiarssoiii, where Mesonacidae appear to be lacking, 

 and farther up the transition beds, in which Lower and Äliddle Cambrian 

 forms are mingled together (Page 98). Although the faunistic transition 

 cannot be studied in detail on account of lack of good profiles, there does 

 not appear to be an}- break in a faunistic sense. 



On the other hand, at several places in Sweden, e. g. in \'estergöt- 

 land (page 107) there is reason to suspect lost intervals in the series. Such 

 are always convenient to fall back upon, but are not always justified. 



But where then is the Protolcnus fauna in Scandinavia? 



In our opinion this remarkable fauna did not penetrate into the Fenno- 

 skandinavian sea. We therefore believe that our uppermost zone with 

 Strenuella Linnarssoni can be regarded as a parallel, although no greater 

 resemblances can be faunistically proved. It is howexer of importance to 

 notice the remarkable agreement between both faunae, that Mesonacidae 

 already appears to be extinct and Paradoxidae not yet come into existence. 



It might be thought however that another solution than that given here 

 was possible, viz. that the Holmia fauna, and thereby all fossil-bearing 

 Lower Cambrian beds in Scandinavia, are younger than the Callavia fauna. 

 The situation in Shropshire, where the Paradoxides Groomii zone, that 

 possibly lies above the Ølandicus zone, is situated with distinct discordance 

 above the Protolcmis zone might lead to such an interpretation. It might 

 be possible that our marine Lower Cambrian deposits correspond to this 

 lost interval. But we thereby enter into so many difficultés in a faunistic 

 respect that I consider the solution previously given to be the most 

 probable one. 



