A MIDDLE CAMBRIAN FAUNA FROM BENNETT ISLAND 1 5 



Besides the species described above, a few more forms oi Agnostidae seem to be present. 

 As only fragments of young or immature specimens have been found, they however cannot 

 now be interpreted with certainty. 



Agnostus sp. No. 1 



[PI. I, fig. 13)] 



The pygidium figured readily recalls the associated A. nudus Tiyperboreus, which however 

 is devoid of axial furrows. It seems to be related to A, confusus n. sp. (= A. bifuherculatus 

 Brogger, non Angelin, compare pi. IV, fig. 7, 8) and, in part, also to A. cicer Tullbbrg. 

 It differs from both of them in having a more completely semicircular outline and a wider 

 axis (which in A. confusus occupies about a third, in A. cicer less than half, of the total 

 width of the pygidium), and moreover it differs from the former in its elongated (not puncti- 

 form) tubercle, from the latter in the axial furrows being directed backwards and inwards. 



Agnostus sp. No. 2 



[PL I, fig. 32, (33, 34?)] 



Only the specimens figured are known. 



Cephalon subrectangular in outline. Glabella conical, bluntly rounded in front, divided 

 by a transverse furrow into a small anterior lobe and a large posterior lobe, the latter 

 having a second pair of furrows not traversing it and being posteriorly arched and raised 

 into a median tubercle ; cheeks confluent in front of the glabella. 



Two very small cephala (fig. 33 and 34) do not seem to differ essentially from the 

 specimen in fig. 32. They are distinguished from the latter by having the cheeks marked 

 by very faint, radiating striae. This distinction, if not associated with other differences, can 

 hardly be of specific significance. In several Agnosti, e. g. A. laevigatus (Dalm.) and 

 A. pisiformis (L.), such a variation is known. 



This species presents a resemblance to A. arcticus and to A. quadratus Tullb. It is 

 distinguished from both by its more conical glabella, the tubercle being situated more 

 posteriorly, and probably by having smaller basal lobes. 



Agnostus sp. No. 3 



[PI. I, fig. 44a, b] 



The specimen, of which the border next to the thorax is not preserved, may probably 

 be the cephalon of an Agnostus. It resembles A. repandus, but is distinguished from that 

 species by its stronger arching, the front of the glabella being bluntly rounded and the 

 marginal rim wider. 



Agnostus sp. No. 4 



[PI. I, fig. 45] 



The very small specimen may possibly be the cephalon of an Agnostus at an 

 immature stage with the basal lobes still undeveloped. 



