174 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 64 



The species is unusually well represented. The first and best 

 specimens were discovered by Mrs. Helena B. Walcott in 1907 at the 

 south base of Mount Bos worth. 



Formation and locality. — Lower Cambrian : Mount Whyte forma- 

 tion: (35c) drift blocks of siHceous shale supposed to have come 

 from the Mount Whyte formation, found on the south slope of 

 Mount Bosworth, about 500 feet (152 m.) northwest of the Canadian 

 Pacific Railway track between Stephen and Hector, eastern British 

 Columbia; and (35m) (Albertella zone) 3 miles (4.8 km.) south- 

 west of the head of Lake Louise, on east slope of Mount Whyte, 

 Alberta. 



Genus ACROCEPHALITES Wallerius 



Acrocephalites Wallerius, 1895, Unders. Zonen med Agnostus lavigatus 

 i Vestergotland, Lund, Sweden, pp. 52-53- 



The following- is the Swedish diagnosis of the genus : 



Head agrees in form with Conocoryphe. Shell finely and regularly granu- 

 lated. The glabella is slightly conical, bounded on all sides by deep furrows, 

 provided with side furrows. In front of it is found a knob-shaped elevation. 

 The anterior margin is broad with a deep intramarginal furrow. The fixed 

 cheeks are broad. The palpebral lobes are of medium size, situated about in 

 the middle of the cheeks. The facial sutures diverge considerably from the 

 anterior margin to the palpebral lobes, from the latter onward they also 

 continue outward, though somewhat less divergent, to the posterior edge. The 

 movable cheeks are somewhat triangular, provided with spines at the angles. 

 The other parts of the body are unknown. 



As previously pointed out, Acrocephalites occupies about the same position 

 to Solenopleura, Conocephalites (Ptychoparia) , etc., as Ctenocephalus to Cono- 

 coryphe. Thus in Acrocephalites, too, it is the tubercle in front of the fore- 

 head that is the most striking characteristic. But furthermore, other characters 

 are found here, which justify the establishment of the new genus. As only 

 one species is at hand, it is impossible to determine definitely what characteris- 

 tics are to be regarded as generic and what as specific; hence the dividing 

 line between these becomes more or less arbitrary, and the two must accord- 

 ingly complement each other. 



Genotype. — Solenopleura ? stenometopa Angelin, 185 1, Pal 

 Scand., p. 28, pi. 19, fig. 4. 



To the preceding description of the cephalon we may now add 

 the following: 



The boss or swelling in front of the glabella is confined to the 

 area of the frontal limb and does not extend into the frontal border. 

 The boss may vary greatly in the same species, as is shown by A. 

 haynesi (pi. 24, figs. 4, 4a). The fixed cheeks may be narrow as in 



