72 JOHAN KIÆR. M.-N. Kl. 



However, the points of difference are very considerable, and can 

 easily be seen on comparing them in the excellent descriptions and illustra- 

 tions in Walcott's work »Olenellus and other Genera of the Mesonacidae«. 



Elliptoccphala Emmons has a glabella of quite another form, a narrow 

 cranidial brim, and a quite different hypostome. The spine armour of the 

 thoracic segments is differently developed, and the thorax obtains quite a 

 different character b}' the fact that the pleurae of the 5 last segments are rudi- 

 mentary. There thus results a narrowing of the posterior part of the 

 thorax which gives this genus a markedly special appearance. 

 Callavia M.'^tthew also differs very distinctly from the new type by its 

 primitive and markedly narrowing glabella, its powerful intergenal spines, 

 quite near the genal ones and the reduction in the last two thoracic segments. 

 We must emphasize however, that within this genus there exists a conside- 

 rable variation, and the limits have become very uncertain, especially after 

 Walcott's latest discoveries. The intergenal spines thus often appear to 

 be lacking, (e.g. Callavia biirri Walcott), and the hindmost segments also 

 at times have a character differing from that in question, as for instance 

 in the two new and interesting forms Callavia encharis and perfecta which 

 were recently described by Walcott^ 



The powerful occipital spine ma}' be greatly reduced or even lacking. 

 The number of segments also varies greatly, from 23 in the case of Calla- 

 via encharis Walcott, to 18 in the geno-type Callavia Broggcri Walcott, 

 and even 17 in Callavia perfecta Walcott. The genus on the whole 

 approaches ver}' close to Nevadia with which it appears to be geneti- 

 cally related. 



Wanneria, too, exhibits considerable differences, especially in the broad 

 anterior lobe of the glabella, the small eyes, its remarkable twoflapped 

 pygidium, and its spined hypostome. 



Our new genus Kjcriilfia approaches most near to Callavia which has 

 a hypostome that strongly reminds one of the hypostome in Kjernlfm lata. 

 The hypostome attachments also in Callavia are broad, but the hypostome 

 does not appear to be inserted immovably in this genus as is the case 

 with the Scandinavian genus-. I shall refer to this matter subsequently. 

 The frontal lobe of the Glabella, which narrows anteriorly, also reminds 

 one of certain' Callavia forms, although the glabella in other respects is 

 differently formed and more like that of Holmia. 



Other features, again, are reminiscent of those seen in IVawieria, e g. 

 the spinal armour of the segments, and the lack of intergenal spines; these 



^ New Lower Cambrian Subfauna (Smithson. Misc. ColL Vol. 5, No. II, 1913. page 315). 

 2 Walcott, Olenelliis etc., 1910, pL 27, fig. 2. 



