BY JOHN MITCHELL. 439 



Proetus Bowningensis, n. sp. 

 (Plate XVI. figs. 4-6.) 



Head evidently semicircular. Grlabella large, semi-conoid and not 

 distinctly marked off by the axial grooves, the lateral furrows 

 feebly present, neck fuiTOW shallow *nd wide, width between the 

 eye lobes nearly equal to the length of glabella, fixed cheeks rudi- 

 mentaiy, facial suture rather straight cutting the outer margin 

 nearly at right angles, and the posterior margin rather near to the 

 glabella. The glabella and tail are about equal in length. Eye 

 crescentic. Of the thorax I have only distinguished fragments. 

 In these the sulcus is strongly marked, and terminates short of the 

 extremity. 



Pygidium semi-elliptical, about | as long as wide, the axis very 

 conspicuous, sides rather perpendicular, top arched or convex, 

 with 7 or 8 rings visible, those towards the extremity indistinct. 

 The 8 rings are only seen in the largest specimens. Side lobes 1^ 

 times as wide as axis at widest part; they are fairly convex on some 

 pygidia, and in others i-ather flattened (but I think that the convex 

 is the normal character), margin fairly large. Four pleurae of the 

 pygidium strongly indicated in which the sulcus is wide and 

 shallow. 



I give some of the dimensions of one of the specimens figured 

 (fig. 4), which is fairly complete ; but unfortunately it has the head 

 turned back on the thorax and almost covering that part. 



Glabella long ^^in. (6'35 mm.) ; pygidium long ^ in. (6'35 mm.), 

 wide ^ in. (9-5 mm.). Another pygidium (fig. 5) has a length 

 of ^ in., and width of f^, so that the proportion of length to width 

 is variable, arising probably from different degrees of compression 

 suffered by the different specimens. 



This species is obtained from the lower Trilobite Bed of Bowning, 

 associated with several species of Fhacops, Acidasjns, and a Cyphas- 

 2ns, probably identical with the one described above. One of the 

 first-named is either P. longicaudatus or very closely allied to it. 



Note. — Since writing the above description I have examined a 

 larger pygidium of the Bronteus, and find that the second rib from 



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