NO. 5 UPPER CAMBRIAN TRILOBITES RESSER I3 



stratigraphic reasons and further collecting is difficult. It is most 

 closely related to C. badgerensis. 



The incomplete holotype cranidium has a large quadrate glabella, 

 slightly constricted in the middle. The occipital furrow is wide and 

 deep but does not join the dorsal furrow with the same strength. No 

 doubt on the outer surface of the test this furrow was either rather 

 shallow or obscelescent toward its ends. The rear pair of glabellar 

 furrows is somewhat less recurved than in C. badgerensis. The fixi- 

 genes at their widest point are equal to nearly half the glabellar width. 

 In cross section the entire cranidium is somewhat flat, and the 

 palpebral lobes slope gently from the dorsal furrow. The eyes appear 

 to have been rather long but their anterior ends are not preserved. 

 Both the test and the exfoliated portions are smooth. 



Lynx formation; (loc. 190) lyatunga Mountain, Robson Peak 

 District, British Columbia. 



Holotype.—lJ. S.N. U. No. 108644. 



IRVINGELLA ULRICH AND RESSER, 1924 



Irviiigclla Ulrich and Ressek, /;; Walcott, Smithsonian Misc. Coll., vol. 75, 

 No. 2, p. 58, 1924. — Walcott, ibid.. No. 3, p. 98, 1925. — Walcott and 

 Resser, Rep. Sci. Results Norwegian Exp. Novaya Zemlya, No. 24, 

 Videnskp., p. 10, Kristiania, 1925. — Resser, Smithsonian Alisc. Coll., vol. 97, 

 No. 10, p. 33, 1938. 



Iri'ingellina Kobayashi, Jap. Journ. Geol. Geogr., vol. 15, Nos. 3-4, p. 175, 1938. 



Relationships between Irvingclla and the other genera of the 

 Komaspidae have been discussed. Kobayashi erected the subgenus 

 Irvingellina on Charioccphahis tiimifrons Hall and Whitfield. Al- 

 though the brim of that species is not fully typical of Irvingella, 

 owing to the upturned edge forming a rim, its essential structure 

 remains that of a bar and therefore agrees in every respect with 

 Irvingella. The other species that Kobayashi assigned to Irvingellina 

 are referred as follows : Irvingella arctica Walcott and Resser to 

 Parairvingclla; Irvingclla gibba Miller and /. (Irvingellina) pro- 

 tuberans Kobayashi to Irvingella. 



Even though published descriptions of Irvingella are very brief, 

 they continue to be adequate in spite of the addition of many new 

 species. 



Genotype. — /. major Ulrich and Resser, 1924. 



IRVINGELLA SILVESTRIS, new species 

 Plate 2, Figures 22-27 



This average-size plump species is represented at several localities 

 in the Arbuckle Mountains by numerous cranidia. 



