1.916 No. 10. THE LOWER CAMBRIAN HOLMIA FAUNA. 3I 



Corda with form grouped around the type A. aficep/ia/us Bar. have small 

 palpebral lobes more anteriorally situated, whereby the posterior extension 

 of the facial suture becomes distinctly longer and outwardly extended. 



Matthew points out that in these respects Strenuella resembles Ellip- 

 socephalus Zenker. In realit}- these famihes are so closel\' related, especially 

 in the Lover Cambrian, that the boundary between them is uncertain. I 

 shall recur to this subject later on. 



Matthew includes in the genus Strenuella besides the t3-p species 

 stremta Billings ^ also another American form Halliana Matthew, although 

 with doubt. To judge from the illustrations, however, the latter must be 

 referred to Agraulos'-. To the above E. S. Cobbold subsequently added 

 a new species. Str. Salopiensis Cobbold " which belongs to the interesting 

 Protolemis fauna at Comley in Shropshire. The species thus belongs to 

 the uppermost part of the Lower Cambrian. 



We now add several form in the Scandinavian Lower Cambrian, all 

 the species that have been described from this region as Agraulos Corda 

 (= Arionellus Barrandel evidently belonging to this genus. 



The last representative of the genus from the Cambrian of Scandinavia 

 is Agraulos depressus Gronwall "* from the Middle Cambrian (Davidis Zone) 

 in Bornholm. However, the genus does not become extinct, but undoub- 

 tedly continues in the Middle Cambrian Ellipsocephalus forms. 



Thus, although a number of species of this oldest and most primiti\"e 

 type of Ellipsocephalidae are known, our knowledge of their structure is 

 still very imperfect. Indeed, in the majority of cases we only know crani- 

 diums, and these without the free cheeks. Two species only [stremia 

 Billings and Salopiensis Cobbold I are somewhat better known, but even 

 these far from completely. 



Strenuella primaeva Brogger. 

 I PI. IV, figs. 1—4, PI. V, figs. 1-61. 



1871. Arionellus sp. Linnarsson Om nàgra försteningar trän Sveriges och Norges "Primor- 

 dialzone". (Öfvers. K. Sv. Vet. Ak, Fôrh. Pag. 78.1 



Mentions occurrence of Arionellus fragments at Tomten with Hohnia Kjertdfi. 

 No desci"iption. 



^ In the fauna of the Lower Cambrian or Oienellus Zone iPage 6541 W.xLCOxr has 

 described a new variety, nasuta. 



2 Matthew, The Fauna of St. John Group, IV (Trans. Roj-. Soc. Canada, Vol, V.^ 

 1887. Sect. Iv., Page 132). 



3 On Some Small Trilobites from the Cambrian Rocks cf Comley 1 Quart. Journ, Geol. 

 Soc. Vol, LXVI, 1910, page 31). 



* K. A. Gr0nw.\ll, Bornholms Paradoxides lag (Danmarks Geo'. Unders. II Ræk. No. 13,. 

 1902, page 159). 



