38 The Ottawa Naturalist. [June- July- 



cheeks rather wide, smooth, with short spines at the genal 

 angles. Pygidium small, with few traces of segmentation; 

 convex; no border." 



The writer finds from the investigation of the material 

 lately collected by Dr. Raymond that the characteristics given 

 by him as "glabella faintly defined, without glabellar furrows" 

 is neither a generic nor a specific characteristic. The present 

 collection fortunately allows a close comparison of the variety 

 first figured and described by Walcott (5), his holotype, and 

 the plesiotype later figured by him in his description of the Hoyt 

 fauna. Here we have the two varieties closely associated, having 

 lived and died under the same physical conditions. Judging 

 from the few well preserved specimens examined by the writer, 

 not more than nineteen in all, it would seem that the form with 

 the smooth glabella predominated. Further and more careful 

 collecting is necessary, however, before this assertion can be 

 proved. It shotild be noted that Walcott in his first description 

 already noted (p. 276) noticed "two pairs of slightly indented 

 glabellar furrows that curve inward with a slight backward 

 obliquity; on the casts of the interior of the larger specimens 



the furrows are scarcely to be seen ." But he shows n,o 



trace of these furrows in his figure. At any rate the presence or 

 absence of glabellar furrows has in this case at least, nothing to 

 do with the generic classification. We shall have more to say 

 regarding the development of glabellar furrows later. 



Walcott (7) in his second paper gives the following descrip- 

 tion of A gr aulas saratogensis: 



"Head convex, slightly semi-elliptical in outline and 

 terminating in round, short, postero-lateral spines; glabella 

 moderately convex, truncate conical, sides converging slightly 

 towards the broadly rounded front, about ^ longer than wide; 

 marked by two pairs of slightly indented glabellar furrows that 

 extend inward with a slight backward obliquity; on the casts 

 of the interior of the larger specimens the furrows are scarcely to 

 be seen; occipital furrow well defined and arched forward at 

 the centre; occipital segment rising to a short blunt spine at 

 the centre and narrowing toward the sides; dorsal furrow well 

 defined abotit the glabella. Fixed cheeks narrow; anteriorly 

 they merge into the broad, rounded, frontal limb and posteriorly 

 into the short posterior lateral limbs ; palpebral lobes small and 

 situated a little in front of the tranverse centre of the head. 

 The frontal limb about \ the length of the head and curved 

 ,down to the margin without an intervening furrow. Free 

 cheeks convex and somewhat tumid, irregularly triangular in 

 outline and -without a marginal border. The associated pygi- 



