NO. 4 CAMBRIAN TRILOHITES, 2D CONTRIBUTION RESSER 7 



not have been studied by Billings before his report was published. 

 Fortunately, the two species recognized by Billings are clearly dis- 

 tinguishable among the several species represented by the types sent 

 from Ottawa. 



Diagnosis. — Small trilobites characterized by a long and essentially 

 quadrate glabella. Glabella usually quadrate, but sometimes expanded 

 forward ; occupying the entire length of the cranidium. Glabellar fur- 

 rows usually very faint. Brim confined to a narrow concave rim. Fixed 

 cheeks about equal to width of glabella. Eyes rather large, extend- 

 ing somewhat forward of the middle of the head, eye lines present. 

 Free cheeks small, generally with short genal spines. 



Pygidium about the same size as cranidium. Segments fused ; 

 pleural furrows usually well defined. Axis usually well above level 

 of pleural lobes. One to three marginal spines occur at anterior angles. 



Genotype. — Bathynriis parvulus Billings. 



Range. — Lower Cambrian, North America and Asia. 



Species of Bonnia not discussed in this paper include : B. groen- 

 landica Poulsen, B. biisa Walcott, B. hrennus Walcott, and B. fieldcn- 

 sis Walcott. 



Bonnia parvula (Billings) 

 Bathyurus parvulus Billings, Pal. Foss., Geol. Surv. Canada, pt. i, p. i6, 



fig. 21, November i86i. 

 Bathyurus senectus Billings (part), idem, fig. 20 (fig. 19 = 5. senccta). 

 Bathyurus senectus Matthew (part), Trans. Roy. Soc. Canada, 2d ser., vol. 



3, sec. 4, p. 196, pi. 4, fig. 4b, 1897 (figs. 4, 43= B. senecta). 

 Dorypygc parvula angifrons Matthew, idem, p. 197, pi. 4, figs. 6, 6a, 1897. 



It has been difficult to clear up the confusion of species grouped 

 under the few named forms of Bonnia, but with Billings' and Wal- 

 cott's types in hand solution of the problem is possible. The fore- 

 going synonomy shows how this was accomplished for B. parvula, by 

 confining the species to specimens from Labrador available to Matthew 

 in 1897. Inasmuch as Dorypyge parvula and Matthew's variety angi- 

 frons are quite distinct species, an eflfort was made to retain both 

 names, but since the same specimen was evidently used as the type for 

 both, they must be regarded as synonyms, and a new name must be 

 given to Matthew's B. parvula. This conclusion is inescapable when 

 the original labels are read, for they state that the specimen to which 

 Matthew gave the varietal name was collected by Richardson in 1861, 

 whereas the other specimens identified by Billings and figured by 

 Matthew as D. parvula were collected by T. C. Weston in 1872. 

 Therefore, Billings' name must be restricted to the fossils he had 

 available when he described his species in 1861. Moreover, applica- 



