A New Phyllocarid Crustacean. 207 
simple, slender, longitudinally elongated and acutely pointed, 
averaging six millimetres in length by about one mm, in 
breadth at the base: the three pairs of spines about equal 
in length, though the two lateral ones are placed farther 
forward than the central and terminal pair. Surface mark- 
ings entirely unknown. 
This genus and species are based upon upwards of fifty 
specimens collected from a band of shale of Middle Cam- 
brian age, at Mount Stephen, near Field station on the 
Canadian Pacific Railway. Two of these specimens were 
collected by Mr. R. G. McConnell, of the Geological Survey 
of Canada, in 1888, and the remainder by Dr. H. M. Ami, 
of the same Survey, in 1891. ‘The species seem to have been 
somewhat gregarious in its habits when living, for upwards 
of twenty specimens of it are exposed on the surface of a 
large slab of shale collected by Dr. Ami at this locality, and 
fourteen upon that of another. It is associated with num- 
erous species of trilobites, brachiopoda, etc., most of which 
have been described by Dr. Carl Rominger and Mr. O. D. 
Walcott. All the specimens of A. Canadensis are crushed 
quite flat laterally and oceur as obscurely defined and ex- 
tremely thin impressions of the body segments, with the 
tail, the latter usually:a little twisted, on each of the surfaces 
exposed by splitting pieces of the shale. 
The generic name Anomalocaris (from av ojoros, unlike,— 
napis, a shrimp, 2.é., unlike other shrimps) is suggested by 
the unusual shape of the uropods or ventral appendages of 
the body segments and the relative position of the caudal 
spines. 
Only three genera of Phyliocarida have previously been 
recorded as occurring in the Cambrian rocks of Kurope or 
America, These are Ceratiocaris, McCoy (1848); Hymeno- 
caris, Salter (1853); and Protocaris, Walcott (1884). To 
these may now be added Anomalocaris, which differs from 
the other three genera of Cambrian Phyllocarids in the 
following particulars. In Ceratiocaris the caudal appendages 
consist of a median telson or style, and two lateral stylets. 
Further, although ventral appendages to the body segments 
