314 



Anomalocaris Canadensis, sp. nov. 



Fig. 20. Anomalocaris Canadensis.— Oxxt\ ne of a specimen in which nine 

 of the abdominal segments are preserved, besides the caudal segment. 

 Natural size. 



" Body, inclusive of the tail, elongated, slender, decreasing slowly in 

 size from the anterior to the posterior end, rather strongly curved pos- 

 teriorly and nearly straight anteriorly, the length of the portion preserved 

 varying in diflferent specimens from nine to ten centimetres (as measured 

 at about the midheight and following the curve of each), and the height 

 or depth at the imperfect anterior end, from twelve to seventeen milli- 

 metres, exclusive of the ventral appendages. Body or abdominal segments, 

 which, in all the specimens collected are abnormally flattened laterally, a 

 little higher or deeper than long, broader above than below, the pair of 

 ventral appendages proceeding from each, nearly equal in height or depth 

 to the segment itself. These appendages are straight and prolonged 

 downward at almost a right angle to the main axis of the body, for 

 although there is a slight divergence in each pair, neither are directed 

 . distinctly backward nor forward. Between each pair of segments there is 

 evidence of a wedge-shaped or very narrowly triangular lateral area or 

 interval, which is broadest or widest below and does not seem to extend 

 quite to the dorsal margin. At the posterior end the segmentation is 

 very obscurely defined. Caudal spines, which are simple, slender, longi- 

 tudinally 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 for- 

 ward than the central and terminal pair. Surface markings entirely 

 unknown. 



" This genus and species are based upon upwards of fifty specimens 

 collected from a band of shale of Middle Cambrian age, at Mount Stephen, 

 near Field station on the Canadian Pacific Railway. Two of these speci- 

 mens 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 



