34 ROYAL SOCIETY OF CANADA 



The glabellar liin-ows and outline of the glahella are nf»t well shown 

 in l)r. Jxoeniinger's tigure. The glabella is wider at the 2nd and 3rd 

 furrows than elsewhere. The posterior furrows are each double and 

 consist of an inner section, posterior, and an outer one, anterior, the two 

 being connected by a shallow depression : the two next furrows cor- 

 respond in length and couree to the outer part of the first furrow, but 

 each has a small distinct pit near the edge of the glabella ; some well 

 preserved heads show a smaller pit on the slope of the glabella in front 

 of the ocular fillet, indicating a fourth furrow as in Parudoxides, this little 

 j)it is often obsolete. 



The arrangement of the glabellar furrow.s and form of the glabella 

 in this species is not unlike that of ParahoUnella limiti,^, Briig., of the Cera- 

 tojiyge limestone in Sweden, which species also has a slight indication of 

 a fourth glabellar furrow ' while the pygidium is comparable with that 

 0Ï ParaboUna heres, Brcig., except that this species has usually one somite 

 less in that section of the body.- The latter species also has a rugulose 

 ornamentation of the cheeks (both fixed and mobile) similar to what we 

 find on examples of JV'. serratus. ParaboUna heres belongs to the Peltura 

 fauna. 



The occipital ring bears a stout spine behind. 



The pygidium, as Roeminger says, has five annulations, but the 

 posterior one is of extra width, and has the spine in the middle, it there- 

 fore represents two somites ; a partly grown individual shows a furrow 

 across the middle of this ring. 



In his figure of the hypostome Dr. Eoeminger does not show the 

 posterior lobe, which is narrow and crescentic, and is indicated b}^ a 

 shallow furrow on each side near the back of the hypostome. The 

 hypostome of 0. Klotzi is very like this. 



Walcott has identified this species with 0/enoides Nevadensis, but it 

 appears to me that the two must be ditierent. The comparison can only 

 be made between the thoraces of the two species, for 0. Nevadensis has 

 no head and only a broken pygidium. The mos-t striking differences are 

 these : In 0. Nevadensis the rachis is wider than the pleura within the 

 geniculation, in the Mount Stephen species they ai-e equal. In the 

 former there is a wide furrow going straight out on the pleura, in the 

 latter there is a narrow oblique furrow. This is not well shown in 

 Eoeminger's figure, but it is clear in all the specimens I have seen. That 

 this representation of the furrow is not an accident in the figure of 

 0. Nevadensis is clear, because Meek calls special attention to it, and 

 makes it his chief reason for separating Olenoides from Paradoxides. 

 This form of furrow is that of Dorypyge as seen in D. Dawsoni. 



' Die Silurischen Etagen 2 und W, pi. iii., fig. 2, Christiania, 1882. 

 '^ Orn Acerocarczonen, Moher^çand Millier, Stockholm, 1898, Tafl. 12, fig. 11, T.itl. 14, 

 flR. i:^. 



