22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 97 



Locality 55c. L.akeview ; (loc. 3711) Lakeview, Pend Oreille Lake, 

 Idaho. 



Cotypes. — U.S.N.M. nos. 70235-7; plesiotypes, no. 95041. 



BYTHICHEILUS, n. gen. 



Trilobites of less than average size. Cranidium rather large. 

 Glabella well defined except in front where the dorsal furrow 

 coalesces with the depression in the brim. Fixigenes about as wide 

 as the glabella. Eyelines formed by abrupt depression of anterior 

 fixigenes. Eyes rather large, situated back of the cranidial midpoint. 

 Brim less than one-third cranidial length. Narrow, striated upturned 

 rim clearly defined. Preglabellar area depressed in a peculiar man- 

 ner, which suggests generic name. Libragenes narrow with moderate 

 genal spines. Striated rim sharply upturned almost to the tip of the 

 genal spines. 



Thorax with 14 segments, rather straight, parallel to each other, 

 divided evenly by pleural furrows and bent down rather abruptly at 

 geniculation. 



Pygidium small, completely fused, with dorsal furrow shallow and 

 not clearly defined around the rear. 



Genotype. — B. typicuni, new species. 



BYTHICHEILUS TYPICUM, n. sp. 



Plate 6, figs. 1-4 



The generic description and illustrations present the specific fea- 

 tures adequately. 

 Locality 55c. 

 Holotype and paratypes. — U.S.N.AL no. 96537. 



BYTHICHEILUS ALVEATUM, n. sp. 



Plate 6, figs. 8-10 



This species differs from B. typicuni in having a longer depression 

 in the preglabellar area, a less upturned rim, less indentation of the 

 front of the glabella by the median depression, and stronger eye- 

 ridges due to the more abrupt slope of the brim. 



B. alvcatuni is characterized by a curved anterior margin, fixigenes 

 about three-fourths as wide as the glabella, and by a depressed pre- 

 glabellar area. Exfoliated specimens show pronounced glabellar fur- 

 rows and strong eyelines. 



Locality 55c. 



Holotype and paratypes. — U.S.N.M. no. 96538. 



