199 



DiKELOCEPHALUS SELECTCS. (N. gp.) 



Description. — The form of the glabella in this species is the same as 

 that of B. Sesostris, with the following differences : The neck furrow and 

 the posterior glabellar furrow are straighter, and terminate in the dorsal 

 furrow. The width of the front margin of the head before the glabella 

 is one-fourth the length of the glabella, and has a depressed convex rim 

 one line wide, in a specimen in which the glabella is five and a half lines 

 in length. The eye is somewhat larger than that of D. Sesostris, and 

 with its centre situated just behind a line drawn across the head at the 

 mid-length. 



These difierences give to the glabella a distinct aspect, but further 

 discoveries may show that this, with the one mentioned as occurrino- at 

 Whitehall, in New York, are all varieties of D. Sesostris. 



Locality. — In the same bed with D. Sesostris. 



DiKBLOCBPHALUS MiSSISQUOI. (N. Sp.) 



Description. — Pygidium resembling that of D. magnificus ; anterior 

 margin rounded in the middle half, then curving backwards and gradually 

 merging into the sides, which become nearly straight, and spreading out- 

 wards at an angle of about 30° with the longitudinal axis ; with this 

 direction they extend backwards a short distance beyond a line drawn 

 across at the apex of the axis or middle lobe. The posterior margin of 

 the pygidium is not preserved in the specimen. Axis short, conical, con- 

 vex, with apparently three rounded segments, .besides a terminal one, which 

 is triangular and gradually merges into the general surface behind. Side 

 lobes gently convex in the central region, gradually becoming flat behind. 

 There are four depressed convex ribs on each side, all spreading a Uttle 

 outwards. 



Length 6 lines, and as the posterior margin is not preserved, when 

 perfect it was a little longer ; greatest width, on a hue drawn across at 4 

 lines from the front margin 9 lines ; length of axis about 3 lines ; width 

 of the same at the front margin 2 lines. 



As before stated, this pygidium resembles that of D. magnificus. It 

 differs in having the ribs at the side nearly flat and considerably divergent, 

 giving a much greater proportional width. 



Locality and Formation. — Phillipsburgh ; (limestone) B 2, section 

 Geo. of Can., p. 844, Quebec group. 



Collector.— Dv. J. M. Hall. 



