532 Dr. H. Woodicard — M. Cambrian Fossils of the Rockies. 



which the coalesced pleurse abut. There are about eleven well- 

 marked coalesced segments in the pygidium, and their backward 

 curvature is much greater than that of the free thoracic segments, 

 gradually increasing more and more towards the extremity of the 

 tail, where they meet the axis at a very acute angle indeed. 



When comparing 0. Klotzi with our English forms of Ogygia one 

 is led to the conclusion that the earlier forms such as 0. Selwyni, 

 Salter, and 0. peltata, are probably nearer the species from Mount 

 Stephen than is 0. BucM ; but that is not the opinion of Mr. Walcott. 

 In any case 0. Klotzi must be considered as a remarkably specialized 

 form, to be met with in such early rocks as the Middle Cambrian 

 of Mount Stephen, and has led Dr. G. F. Matthew to suggest that 

 this bed may be really of Upper Cambrian age. 



Walcott says of this Trilobite : " This is a fine large species, and 

 distinct from any known to me from the Cambrian terrane. It is 

 more a type of the second fauna than of the first ; and its reference 

 to the genus Ogygia is in accord with its general characters. It 

 differs, however, in the important feature of having an ocular ridge 

 extending from the anterior margin of the eye to the dorsal furrow 

 beside the glabella. The palpebral lobe is also more narrow and 

 elongate than the eye of most species referred to Ogygia. All other 

 parts of the head, thorax, and pygidium relate it more closely to 

 Ogygia than to any other genus. The oldest known species of the 

 genus, 0. Selwyni, Salter, from the Arenig terrane of Wales, is not 

 quite so closely related in form to 0. ? Klotzi as to the 0. BucM from 

 the Llandeilo terrane." 



" It is remarkable that a genus showing so little variation from 

 Ogygia proper should occur at an horizon so much lower, in an 

 area separated by over 5,000 miles from that in which the genus 

 flourished at a later period in geologic history." 



Having regard to the fact that Ogygopsis Klotzi differs from 

 Ogygia proper in having a well-defined ocular ridge and a narrow 

 palpebral lobe, it seems convenient to separate this Rocky Mountain 

 form generically from the other examples of Ogygia as represented 

 by 0. BucM, more especially as the latter occurs in beds so much 

 younger than the Middle Cambrian, in which 0. Klotzi is found (see 

 C. D. Walcott, Proc. U.S. National Museum, 1888, vol. xi, p. 446). 



Bathturisous Howelli, Walcott, 1886. 



BatMjuriscm EoivelU, Walcott, 1886 : Bull. U.S. Geol. Sury., No. 30, p. 216, 



pi. XXX, figs. 2, 2a. 

 JEmholimus rotundata, Eominger, 1887 : Proc. Acad. Nat. Sci. Philad., p. 16, pi. i. 

 EmboUmus rotimdatus (Rom.), Walcott, 1888 : Amer. Journ. Sci. [3], vol. xxxvi, 



p. 165 ; referred to B. Sowelli. 



There are six nearly complete examples of this species (three 

 showing the free cheeks in situ, more or less perfectly) and one 

 detached pygidium, all from Mount Stephen, in Mr. Whymper's 

 collection. The figure represents the species one-fourth larger than 

 natural size. 



This species might, at first sight, be confounded with junior 

 specimens of 0. Klotzi, but on closer examination it will be found 



