Dr. H. Wooclivard — M. Camhrian Fossils of the Rockies. 539 



abdominal or pygal segments correspond with those of the pleurae, 

 but they diminish very rapidly to the extremity of the tail. The 

 axis of all the free thoracic segments and perhaps the first of the 

 coalesced caudal segments appear to have each supported a central 

 spine, as in Zacanthoides typicalis, Olenellus (Holmia) Kjendfi, Holm, 

 0. Gilberti, Walcott, Olenellus Callavei,^ 0. (Holmia) Broggeri, and 

 many other Cambrian forms of Trilobites. 



If one is surprised to find a genus such as Ogygia Buchi in the 

 Llandeilo Flags of Builth represented in the still earlier Middle 

 Cambrian fauna by 0. Klotzi at Mount Stephen, B.C., it is equally 

 remarkable to find Zacanthoides spinosus at Mount Stephen, B.C., 

 and Z. (0.) typicalis (in Middle Cambrian), Pioche, Nevada, U.S.A., 

 so closely resembling and preceded by such a form as Olenellus- 

 (Holmia) Kjendfi in the Lower Cambrian of Norway,^ which, although 

 belonging to another genus, was clearly an ancestral form. 



Concerning the genus Embolimus Mr. Walcott writes^ :—" The 

 generic name Embolimus was given by Westwood'to a genus of 

 Hymenoptera in 1833.' It was spelt Emholemus by Westwood, and 

 was corrected by Professor Agassiz to Embolimus in his Nomenclator 

 Zoologicus. ; 



" The first species named under this genus by Dr. Eominger, 

 Embolimus spinosa, was described as Olenoides spinosus in 1886, 

 and the second species, Embolimus rotundatus, as Batliijuriscus 

 Howelli. 



" When studying the Georgina fauna in 1885, I found that the 

 genus Olenoides was probably the same as the genus Dorypyge of 

 Dames. Wishing more material for comparison I left all the 

 species under the genus Olenoides. A large, fine species of the 

 genus Olenoides was collected in the Cambrian shales of Northern 

 Alabama in 1886, which proved conclusively that Dorypyge was 

 founded on a species congeneric with the type of Olenoides. I then 

 recognized that the species Olenoides typicalis, 0. spinosus, 0. levis, 

 and 0. fiagricaudatus formed a distinct generic group, which I was 

 preparing to illustrate when Dr. Eominger's paper appeared. As 

 the generic name proposed by him is preoccupied I suggest the 

 name Zacanthoides, including in it Z. typicalis, Z. spinosus, Z. levis, 

 and Z. fiagricaudatus. The species remaining under Olenoides 

 are 0. Nevadensis, 0. Marconi, 0. quadriceps, and 0. Wasatchensis. 

 After comparing specimens I found that Embolimus spinosa, Eom., 

 = Zacanthoides spinosus, Walcott ; Embolimus rotundata, Eom., 

 = Bathyuriscus Howelli, Walcott ; Ogygia serrata = Olenoides 

 Nevadensis, Meek; and that the last two, Gonocephalites Cordillerce, - 

 'Roin.,=z Ftychoparia Cordillercs, 'Rom. (sp.), and Ogygia? ? Klotzi, 

 Eom., are new additions to the previously known Cambrian fauna." 



^ Olenellus Callavei, Lapworth: Geological Magazine, 1891, pp. 529-536, 

 Pis. XIV and XV. 



2 G. Holm, " On Olenellus Kjendfi " : Foren. Forhandl., 1887, Bd. ix. 



2 C. D. "Walcott, "Cambrian Fossil from Mount Stephen, N.W. Territory of 

 Canada": Amer. Joui-n. Sci. [3], 1888, vol. sxxvi, pp. 161*-166. 



