202 TRANSACTIONS OF THE [May 18, 
Size.—Height of the summit of the dorsal curve above the 
aperture, 3 mm. Length of chord of dorsal curve, 34 mm. 
Length of aperture, 45 mm. 
Horizon and Locality.—In the fine, dark gray shales of Div. 
1 d.1, at Porter’s Brook, St. Martin’s. Not infrequent. 
This species may be compared with S. Cornucopia Salt. of 
the Menevian Group, in Wales; it differs in having a wider aper- 
ture and more strongly arched dorsal slope. 
Six years ago a close examination of the surface characters 
led the author to refer this object (and its genus) to the Crus- 
tacea, chiefly from its punctate surface and from the fact that 
the sculpture showed more distinctly on the inner surface than 
the outer. The shell substance was also found to be calcareo- 
corneous, like that of the trilobites and other Crustaceans. 
Var. Rapiata. (Plate XIV., fig. 2.) 
Stenotheca radiata. Trans. Roy. Soe. Can., vol. iii., pt. iv., p. 
51s ple wis, dies 12: 
Outline lenticular, more strongly arched on the apertural than 
the dorso-ventral side; dorsal slope about three times as long as 
the ventral; apex larger and more prominent than in the type; 
ventral slope more concave; a sulcus about one-third from the 
dorsum, arching from the apex to the base, usually delimits the 
dorsal zone from the rest of the plate. There are about five 
irregular, concentric ridges on the apical part and ten more dis- 
tinct and regular ones on the rest of the plate. 
Sculpture.—Differs from that of the type in the general ab- 
sence of the chevron pattern (though in a band extending along 
the middle and at the outer margin this pattern sometimes ap- 
pears), but generally the arrangement of the ridgelets is irreg- 
ularly linear. 
Size.—Usually somewhat smaller than the type. 
Horizon and Locality.—In the gray shales of Div. 1 ¢ at St. 
John; rare; also in the dark gray shales of Div. 1 d!, at St. 
Martin’s ; more common. 
The example of this variety from Div. 1 ¢ is smaller than 
those from Diy. 1 d!, and has striz radiating from the apex. 
A comparison of these little plates with the triangular plates 
of Plumulites will show that they are much alike, the essential 
differences being the doubling of the plate in Stenotheca, its 
broader aperture and the insertion of additional ridges near the 
dorsum. The Cambrian fossils have the same sharpness and 
close opposition of the ridges, and in a less distinct degree the 
radial banding from the apex. Though we noted the points of 
