3l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



OLENELLUS TRUEMAKI, new species 

 Plate 54, figs. 2-10 



This species differs from Olcnellus flwmpsoiii (Hall)* and 0. ,i^;7- 

 bo'ti Meek ' in having shorter palpebral lobes and eyes, smaller and 

 shorter plural lobes of the third thoracic segment, and in having a 

 more coarsely reticulated outer surface of the test, in the latter char- 

 acter resembling 0. reticulatus Peach.' It differs from the latter and 

 O. lapzi'orthi Peach ^ in having a stronger rim about the cephalon, the 

 anterior glabellar lobe closer to the frontal rim, and a broader thorax 

 and smaller, shorter pleural lobe on the third segment. The third 

 thoracic segment is distinctly larger than the others in all specimens ; 

 proportionally it decreases in size from the young to the largest adults, 

 as may be seen by comparing figure lo and figure 2, plate 54. 



The hypostoma has a denticulated posterior margin similar to that 

 of Pccdciimias transitans' and Wanneria liaUi." It appears to have 

 been attached to the doublure by its anterior margin and not by a 

 process as in Pccdemnias transitans. 



The specimens of this species are abundant and usually well pre- 

 served. The largest cephalon collected has a width of 50 mm. and a 

 length of 22 mm., and the entire dorsal shield has a length of 56 mm. 

 exclusive of the spine-like telson. 



The specific name is given in memory of Dr. J. i\I. Trueman, of the 

 Geological Survey of Canada, a most promising young geologist who 

 was drowned in a canoe accident that occurred (June 24, 1912) while 

 he was showing me the Huronian fossil-bearing limestones of Steep- 

 rock Lake, Ontario, Canada. 



Forwation and locality. — Lower Cambrian: (6ik) ]\Iahto forma- 

 tion ; dark, hard siliceous shale ; northeast base of Alumm Peak above 

 JMural Glacier on west side of Hitka Pass, 6 miles (9.6 km.) in a 

 direct line north of summit of Robson Peak and northwest of Yellow- 

 head Pass, in western Alberta, Canada. 



^ Smithsonian Misc. Coll., Vol. 53, No. 6, igio, pi. 35. 



" Idem, pi. 36. 



^ Idem, pi. 39. 



■* Idem, pi. 39. 



' Idem, pi. 34, fig. 8. 



" Idem, pi. 31, fig. 9. 



