igiö. No. lO. THE LOWER CAMBRIAN HOLMJA FAUNA. 53 



Other kindred forms; we have further the diffonuis series, to which possibh' 

 belong the form ciradits Broggek which was described as Ellipsoceplmlus 

 and the Agranlos holocephalus group, and possibly others. The forms 

 in the Chinese Middle Cambrian, which Walcott termed Inoyia, — Wal- 

 cott's genus Levisia is also probably related — can scarcely belong to 

 a different genus. Several of these groups are differentiated as marked ground 

 and mud fossorial forms {ceticephahis Barr., diffonnis Ang. and circiihis 

 Broggeri. The last named representatives are found in the lowest 

 ordovicium \A. Saratogcnsis\<J \\.coit\^ . I am inclined to derive this some- 

 what extensive group of Agrauhid forms from Ph'choparia-Xxke Lower 

 Cambrian forms. I am thinking particularly of such forms as Walcott 

 described from the Lower Cambrian of North America. Several of the So/eiio- 

 pleura forms too, that were described from those regions, appear to be 

 related, whilst others ( S olcuo pleura Harvcyi and Hoivleyi) should rather be 

 considered as related to Strenuclla '-. 



Agraidos and related genera must therefore be regarded as a group 

 of forms that have developed parallel to Strenuclla and Ellipsocephalus 

 and differentiated in a similar manner, on account of adaptation to corre- 

 sponding conditions of life, without having an}' genetic connection with them. 

 Therefore for the present I cannot presume to include Agraulos and the 

 genera mentioned that are related to it with the family Ellipsocephalidae . 



There are, however, other genera that undoubtedly should be regarded 

 as belonging to that family. 1 hese are first and foremost forms that are 

 described under the names Micniacca Matthew ^ and Mohicaua Cobbold"*. 

 In the structure of the cranidium these show so close agreement with 

 Strenuclla that there can scarcely be any doubt that they are closely related 

 to that genus. 



What are known as the Aneniocare forms, too, as Cobbold describes 

 in the same work, appear to be near. Nor has any proof been brought 

 forward to show that their pygidiums have resembled those of Aneniocare. 

 The similarity to Aneniocare, as emphasized by Cobbold, is in my opinion 

 not surprising, as 1 consider this genus also as a further development of 

 the same oris;inal stock. 



1 New York Potsdam-Hoj'at Fauna Smith's Misc. Col!. Vol. 57, No. 9, 1912. p. 269. 



~ Olenellusl'auna, pi. 96 — 98. 



'■' The Protolemis fauna. (Transact, of the New York Acad. Sc. 1894, Vol. XXIV, p. i4i.> 



See also E. S. Cobbold: On Trilobites from the Cambrian Rocks of Comley. (Quart. 



Journ. Geol. Soc, 1912, Vol. 66, p. 261. 

 •* Op. cit. p. 44. 



