320 



lected, has the cheeks abruptly elevated from the bottom of the dorsal 

 furrow at the side of the glabella to the eye. The pygidium has a very 

 small axis, and the side lobes are nearly flat. 



2. B. nitidus. — The glabella and eyes are surrounded by a semicircular 

 groove, and the whole of the margin in front of the apex of the glabella is 

 concave {ante, p. 265, fig. 249). 



3. B.formosus. — Only one-third of the space in front of the glabella is 

 concave ; in this species the concave border is at least half the width of 

 the same space. 



4. B.fraternus. — The head is more convex, while the front part of the 

 glabella is more depressed, being on a level with the general surface. 

 The pygidium is, also, shorter, the axis wider and not elevated at the 

 apex. 



5. B. validus. — Head strongly convex ; front of the glabella not ele- 

 vated ; the whole of the side lobes of the pygidium concave, and the axis 

 not elevated at the apex. 



Of all the above, B. nitidus and B. marginatus seem to be most closely 

 allied to B. ei-pansus. They form a remarkable group, and it may yet 

 be found necessary to unite them all into one polymorphic species. 



{jocality and Formatiun. — Stanbridge, range 6, lot 20 ; Quebec 

 gi-oup. 



Collector.— T. C. Weston. 



Other Species of Bathyurellus. 



The following are named provisionally from specimens of the pygidium. 



1. Bathjurellus rarus. The specimen is a flat and nearly perfectly 

 semicircular pygidium, nine lines in length and seventeen in width. There 

 are obscure indications of an axis extending one-third the length ; it is 

 scarcely elevated above the surface. There is a faint concave depression 

 all round near the margin and the central one ; half of the whole upper 

 surface is slightly convex. Surface apparently smooth. It was collected 

 in the upper part of limestone No. 2, at Point Levis, Quebec group, by 

 T. C. Weston. 



2. Bathyurellus litoreus. — Pygidium nearly semicircular, anterior angles 

 obliquely truncated, sides and posterior margin rounded to the curve of a 

 semicircle ; axis not quite the whole length, from one-fourth to one-third 

 the whole width, conical, the apex moderately well defined. There is an 

 obscure groove close to the anterior margin on the axis and side lobes, but 

 otherwise the whole surface is smooth. The side lobes are nearly flat, with 

 a barely perceptible slope to the margin. Occurs with the former and also 

 in band D, on the beach at Point Levis. 



