664 



MR. B. N. PEACH ON THE FAUNA OP THE [NOV. 1894, 



all the American species as yet described is that the posterior 

 angles of the eye-lobes are set much farther out from the edge of 

 the glabella in this species — a character which it shares in common 

 with all the other species in the collection under review. From 

 Olenellus Thompsoni and 0. Gilberti, which it most nearly approaches, 

 it is further distinguished by the line of tubercles ranging from 

 the occiput, and extending down the axes of all the segments. 



Table op Measurements of Olenellus Lapworthi. 





M. 4085 d . 

 PI. XXIX. fig. 1. 



M. 4078 d . 

 Pl.XXIX.figs.2&2,a. 



Length of head-shield and first 



mm. 

 25 



• mm. 



20 



9 



20 



Length of head-shield and body- 

 segments, exclusive of telson . . . 



13 

 26 







The figures at the top of the columns are the registered numbers of the 

 specimens in the books of the Geological Survey of Scotland. 



Olenellus Lapworthi, var. elongatus, nov. (PI. XXIX. figs. 3-6.) 



This name is proposed to include the more elongated forms of 

 this species. Fig. 3, PI. XXIX., represents a nearly complete 

 specimen enlarged two diameters. In general contour of the body, 

 it is somewhat more elongated than 0. Lapworthi. Its specially 

 distinguishing feature, however, is the unusually developed pleural 

 spines of the third body-segment, which not only extend much 

 farther backward than in that species, but are curved inward in 

 the same manner as in Olenellus Gilberti, a species found on the 

 side of the Rocky Mountains opposite to that wherein 0. Thompsoni 

 has been found. Like the former, it appears to have terminated 

 in a long spear-like telson, portion of which is seen in fig. 3, 

 PL XXIX., which is too imperfect to show the details of its con- 

 figuration or to indicate its probable length. 



Several fragments of the third body-segment of this form are 

 preserved in the collection under review. The test of this variety 

 is ornamented with a sculpturing similar to that of 0. Lapworthi. 

 A portion of a labrum which seems to belong to this variety is 

 reproduced in PI. XXIX. fig. 5, magnified two diameters. 



The specimen from which fig. 3, PL XXIX., was taken gives the 

 following measurements : — 



Full length without telson 22 mm. 



with „ 25 „ 



Lengtb of carapace 10 ,, 



Breadth of do 19 „ 



„ body across third segment ... 14 „ 



