662 ME. B. N. PEACH ON THE PAUNA OP THE [Nov. 1 894, 



At the same time, they made a short search at this exposure of the 

 ' Fucoid Beds,' which, although they lie not far beneath the outcrop 

 of the ' thrust-plane/ are comparatively free from disturbance. 

 Mr. Home found a fine specimen of Acrothele subsidua, a small 

 brachiopod which is associated with the Olenellus-fa,u.na. in Utah 

 "and Nevada. Mr. Macconochie was soon afterwards despatched 

 to Kenlochewe, and having had every facility afforded him by 

 Mr. Cazalet, the tenant of the forest, soon struck upon the beds 

 which yield Olenellus, and made a fine collection. He likewise 

 returned to the outcrops in Glen Logan and proved the occurrence 

 of Olenellus in the ' Fucoid ' Shales there ; but, in consequence of 

 the strata being much affected by post-Cambrian movements, the 

 specimens are tod indistinct for description. The collections thus 

 secured were placed in my hands, as acting Palaeontologist to the 

 Geological Survey of Scotland, and, by permission of the Director- 

 General, I now beg to lay before this Society as a sequel to the 

 former paper * a description of the trilobite-remains. 



II. Description op a new Sub-genus and some new 

 Species op Trilobites. 



The trilobite-remains in this collection consist of several hundred 

 fragments, chiefly head-shields, a few nearly complete individuals 

 with both head-shields and body-segments attached, several minor 

 fragments affording good material for study, and a large number of 

 pieoes that may be called scraps. These various specimens enable 

 me to complete the account of the structure of Olenellus Lapworthi, 

 described by me from head-shields alone, as well as to announce 

 the existence of other species of the genus. Moreover, the specimens 

 include numerous head-shields and one almost complete individual 

 that appears to belong to a separate sub-genus. 



Genus Olenellus, Hall. 2 



Olenellus Lapworthi, Peach. (PI. XXIX. figs. 1,2,2a; PL XXX. 

 fig. 7.) 

 Head-shield described in a former paper. 3 Body-segments, 

 fourteen in number, all free, with well-embossed axes divided from 

 the pleura by shallow axal furrows, and each bearing in the mid- 

 line near the posterior margin a small tubercle or short spine. The 

 pleura, which are wide, with thickened fulcral margins, well-marked 

 fulcral grooves, and thickened posterior margins, are bent back 

 suddenly upon themselves opposite the end of the fulcral groove, 

 and terminate in a more or less produced, recurved spine. The axes, 

 which, next to the head-shield, are nearly as wide as the occipital 

 ring itself, carry their breadth down to the third segment ; thence 

 they diminish backward till the axis of the fourteenth segment 

 is a little less than one half the breadth of the first. 



1 Quart. Journ. Geol. Soc. vol. xlviii. (1892) pp. 227-241. 



2 The genus Olenellus !s here used in the restricted sense explained in my 

 former paper, op. cit. 3 Ibid. 



