216 TRANSACTIONS OF THE [May 18, 
paratively smooth ring of the posterior joint of the thorax, and 
in the absence of segmentation in the rachis of the pygidium. 
Size.—Length, 12 mm; width, 5 mm. 
Horizon and locality.—This variety has been found only at 
St. John in Div. 1 c!. The typical fallax occurred here also, 
but is more common at Hanford Brook in Div. 1 c?. 
Var. CONCINNUS. pl. xv., figs. Ja to ec. 
Agnostus vir. var, concinnus, Trans. Roy. Soc. Can. vol. iii., 
pt. iv., p. 70, pl. vii., figs. 4a to ce. 
This form presents the following differences from var. vir.: 
The glabella is more cylindrical, is proportionately longer and 
the cross-furrow is directly transverse. In the thorax the last 
segment carries five distinct lobes, the middle lobes being seg- 
mented. In the pygidium at the anterior end of the rachis, a 
small triangular lobe is faintly defined on each side. This va- 
riety is smaller than in the type. 
Size.—Length, about 9 mm; width, 35 mm.; cephalic shield, 
4x3} mm. 
Horizon and Locality.—The fine dark gray shales of Div 1 d! 
at Porter’s Brook, St. Martin’s, ete. 
Development of the Young.—Both the head shield and pygi- 
dium of the } mm. size have been found in this form. The front 
furrow of the glabella is more distinct than in the preceding 
variety, and the basal lobes are scarcely visible. At 14 mm. 
some heads develop a short furrow from each front corner of 
the glabella, running forward; this furrow is sometimes seen in 
the adult of A. fissus. A head shield 34 mm. has three furrows 
of this kind; one median. 
The pygidium of 4 mm. size already has the marginal fold 
and furrow distinct, but the furrow is not widened backward, 
though the fold is and is cuspidate. The rachis is prominent, 
except behind, and the front lobe is marked off by a shallow 
furrow ; the width of the second lobe is defined by the long axial 
tubercle; behind it isa third lobe, not defined by any furrow, 
weak and at the end sinking below the level of the cheeks, which 
meet and are wide behind it. In this small pygidium there is 
no fourth lobe in the rachis, but this is developed in the 1} mm. 
shield, which differs little from that of var. vir of the same size, 
except that the posterior tubercle has not been observed. 
Var. TRILOBATUS. pl. xv., fig. 9. 
Agnostus partitus (supposed pygidium). Trans. Roy. Soc. 
Can. vol. iii., p. 68, pl. vii, fig. 20. 
