240 TRANSACTIONS OF THE [may 18, 
Occurring at the horizon of this species there is a somewhat 
long semi-circular pygidium which may belong to this species ; 
a young example possesses the following characters. It is one 
and a-half times as wide as long. Rachis narrow and prominent, 
about one-fifth of the width of the shield, and three-quarters of 
its length; two rings are divided off the front by transverse 
furrows, two others are marked by side furrows, and there is a 
posterior lobe twice as long as wide, not reaching the marginal 
fold. The side lobes are tumid and are traversed by transverse 
furrows ; three in front have the appearance of anchylosed seg- 
ments of the thorax; one behind is less distinct, and a fifth is 
faintly indicated. A low, narrow, obscure fold goes around the 
margin of the shield. 
Sculpture.—There are minute scattered tubercle on the cheeks 
and glabella, and minute, rather obscure crenulations on the 
inner surface of the test at the marginal fold. The supposed 
pygidium is minutely granulated. 
Size.—Length of the head shield, 2 mm.; width, 1} mm. 
Horizon and Locality.—In the fine gray shales of Div. le? at 
Hanford Brook and Porter’s Brook, St. Martin’s, N. B., Canada. 
This species has a general resemblance to M. scanicus of the 
Swedish Paradoxides beds as regards the head shield; but if 
the pygidium described above belongs here, the species is more 
nearly related to M. Dawsoni and M. Schucherti; the crenula- 
tions of the margin are similar to those of the section Eodiscus, 
but not so sharply marked or so noticeable. 
Micropiscus Dawson, Hartt. Plate xvii., figs. 5 a@ to e. 
Microdiscus Dawsoni, Hartt. Acad. Geol., 2d ed., p. 564, fig. 
228. 
Microdiscus Dawsoni, Walcott, U. 8. Geol. Surv. Bull 10, p. 
p. 23, pl. ii., figs. 3 and 3a. 
Microdiscus Dawsoni, Trans. Roy. Soc. Can., vol. iii., pt. iv., 
p, 15, pl. viigaigs. 1, a tore. 
Description.— Cephalic shield semilunar, with thickened 
border, crossed by numerous grooves running perpendicularly 
to the circumference. Glabella convex, narrow, rounded in front, 
conical and pointed behind, projecting beyond the posterior 
border, without furrows or occipital groove. Cheeks convex, 
no eyes and no traces of sutures, posterior angles of the shield 
with backwardly projecting spines. Pygidium subtriangular, 
with curved outlines, rounded in front and behind ; middle lobe 
distinctly marked and divided into six segments; lateral lobes 
also divided ; furnished with a narrow border.” 
This is one of the most characteristic species of the P. lamel- 
