NO. 5 CAMBRIAN TRILOBITES 433 



Corynexochus stephcncnsis (Walcott) — Continued. page 



Sb. (X8.) A minute cranidium tentatively referred to this species. 

 U. S. National Museum, Catalogue No. 62717. 



From locality 35k, Middle Cambrian: Burgess shale; i mile (1.6 

 km.) northeast of Burgess Pass, British Columbia, Canada. 



5r. (X2.) Matrix of cranidium. U. S. National Museum, Cata- 

 logue No. 62718. 

 From locality X4S, Middle Cambrian : Stephen formation ; Mount 

 Stephen, British Columbia, Canada. 



Corynexochus minor (Walcott) 3^9 



Fig. 6. (X 6.) Group of specimens on a fragment of shale. U. S. 

 National Museum, Catalogue No. 26703. 

 60. (X8.) Form of hypostoma abundantly associated with this 



species. U. S. National Museum, Catalogue No. 62719. 

 6b. (X 8.) Small dorsal shield with three thoracic segments. U. S. 

 National Museum, Catalogue No. 61730. 



The specimens represented by figs. 6, 6b were illustrated by figs. 7, 

 yb, plate 36, Smithsonian Misc. Coll., Vol. 64, 191 5- 

 6c, 6d. (X8.) Cranidia illustrating variation in form from small 

 specimens 0.5 mm. in length to adult size. U. S. National 

 Museum, Catalogue Nos. 6c, 62720, and 6d, 62721. 

 The specimens represented by figs. 6, 6a-d are from locality i, 

 Middle Cambrian: Manuels River, above Conception Bay, near 

 Topsail Head, Newfoundland. 



Corynexochus senectus (Billings) (see pi. 56, figs, i, la-g) 3^9 



Figs. 7, 7'. (X3-) Dorsal and side views of a partially exfoliated 

 cranidium, with slight indication of lateral glabellar fur- 

 rows. U. S. National Museum, Catalogue No. 62722. 

 ya, 7a. (X3-) An associated pygidium that has been slightly 

 elongated. U. S. National Museum, Catalogue No. 62723. 

 /b. (X3-) Associated pygidium, partly flattened by compression. 



U. S. National Museum, Catalogue No. 62724. 

 7c. (X4.) Associated hypostoma. U. S. National Museum, Cata- 

 logue No. 62725. 

 The specimens represented by figs, ja-b are from locality 6 id, 

 Lower Cambrian: Mount Whyte formation; southwest slope of 

 Mount Shaffer, British Columbia, Canada. 



