670 



B. N. PEACH ON IHE FAUNA OF THE [Nov. 1 894, 



Each of these consists of a well-marked axis, very large in propor- 

 tion to the pleura, from which it is marked off by shallow axal 

 grooves, and bearing a tubercle or small spine in the mid-line near 

 the posterior edge. The axis of the first segment is of about the 

 same width as the occiput, and this width is maintained as far as 

 that of the third segment. From this point they taper gradually 

 backward to the sixth segment, behind which there is a compara- 

 tively sudden contraction, the seventh and eighth segments being 

 much smaller than any of the rest. The pleura, which are almost 

 quadrate in shape, have fulcral ridges and grooves, and spines 

 on their postero-lateral angles. These are small and insignificant, 

 except on the pleura of the third and sixth segments, which are 

 long and strong, and set backward at almost the same angle as the 

 posterior spines of the head-shield. 



From the sudden tapering behind the sixth segment, and from the 

 nature of the pleura of the seventh and eighth segments, which are 

 especially small and set backward, it is inferred that the body 

 never bore many more than those exhibited. The nature of the 

 terminal segment or telson is unknown, though it was in all 

 probability styliform. 



Some of the specimens show that the test was ornamented with 

 a reticulated pattern, as in Olenellus and other early trilobites. 



Table of Measurements of Olenelloides armatus. 





M. 41 U d . 



M. 4116 d . 



M. 4117 d . 



M. 4127 d . 





PI. XXXII. 



PI. XXXII. 



PL XXXII. 



PI. XXXII. 





figs. 1-3. 



fig. 4. 



fig. 5. 



fig. 6. 





mm. 



mm. 



mm. 



mm. 



Length of head-shield and 











eight segments, exclusive 











of spines 



11 









Length of head-shield, ex- 











clusive of spines 



5 



475 



3 



4 



Breadth of do 



4 



2 



45 

 3 



25 



1-75 



4 

 2-5 



Breadth at anterior margin 



„ ,, posterior do. .. 



3 



35 



1-75 



3 



Average length of spines on 













25 



25 



2-5 





Average breadth of axis of 











glabella 



1-75 



1-75 



1-25 



1-75 



Breadth of 1st body-segment 



35 









„ of axis of do 



1-75 









Depth of do 



1 









Breadth of third segment . . . 



3 75 









,, of axis of do 



1-75 











1 









Length of spine on do 



2-25 









Breadth of sixth segment... 



2 











1 









Depth of do 



•75 









Length of spine on do 



1-5 









Breadth of seventh and 











eighth segments 



1 











4 









