Olen. 



490 



(Georgian) limestones at Troy; at Shodack Landing; and at 

 Eeynold's Inn, N. E. of Bald Mtn.. Wash. Co., N. Y.— Note. 

 The fragments of this species cannot be distinguished from 

 fragmeuts of Olenellus thompsoni and Olenellus gilherti^ un- 

 less the chest joints (thoracic segments) are got. 



Olenellus gilberti, of the Eocky Mountains, has not been 



M.C. 



found on the Atlantic side of the continent. Its head exhibits 

 a large range of variation. It has been collected from lime- 

 stone, clay and sand strata, through a section 50' to 300' high, 

 overlying 3000' of Wasatch Mountain red-brown quartzite, of 

 Middle Cambrian age ; in Nevada and Utah in various locali- 

 ties ; and in British Columbia. See Walcott's Bulletin No. 30, 

 U. S. G. S. p. 173. From his numerous figures on plates 18, 19, 

 20 and 21, I have selected pi. 21, fig. 1, normal form of species, 

 except in the unusual prolongation of the third segment, en- 

 larged twice ; fig. 1 a^ shows the actual size ; fig. 2 a^ the actual 

 size of another specimen broadened by pressure in the move- 



