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1896. ] NEW YORK ACADEMY OF SCIENCES. 241 
latus Subzone. The head shields in my examples are broadly 
semicircular ; the glabella and cheeks slope downward in front. 
below the level of the anterior marginal fold, which rises in front 
as a prominent, crenulated, transverse ridge; the glabella ex- 
tends backward into a stout spine, slightly hooked downward at 
the extremity ; the glabella and spine form together a fusiform 
axial lobe tapering to both ends, and the two parts are nearly 
on the same plane. 
The thorax consists of two joints having rounded rings and 
the pleurz have broad furrows directed forward as in Agnostus. 
The pygidium is angled in front, has seven segments in the 
rachis and five ribs on the lateral lobes, of which the posterior 
are strongly directed backward as on the Welsh MM. sculptus, 
Hicks. 
Sculpture.—This species is closely granulated on those parts 
of the test that are raised above the general surface, but not in 
the furrows. 
Size.—Length of head, exclusive of spine, 3 mm.; width, 
4mm. Length and width of pygidium, the same. The occipital 
spine is 2 mm. long. 
Horizon and Locality.—The fine gray shales of Div. 1 c+ at 
St. John, Ratcliff Stream, Simonds’ and Hanford Brook, St. Mar- 
tin’s, N. B., Canada, but nowhere plentiful. 
Development of the Young.—The young head shield in this 
species differs widely from the adult. At the length of 1 mm. 
the front rim is narrow all around and no crenulation is visible ; 
the cheeks are comparatively flat, and there is a flattened area 
within the rim indented with a depressed point in front of the 
elabella, which it touches as in M. Schucherti. The glabella is 
pointed behind but bears no spine. The genal angles are some- 
what pointed. At 14mm. length of head shield, the rim begins 
to widen in front and shows shallow crenulations, and the flat- 
tened area still shows a depression in front of the glabella. The 
genal angles are sharp and the posterior marginal fold broadens 
at the end and is upturned as in WM. Schucherti. The glabella 
has a long anterior lobe, as MW. speciosus has in the adult stage. 
In the later moults the strongly crenulated widened margin and 
the development of the occipital spine easily distinguish this 
species from the former of those above named, and the breadth 
of the shield and wide anterior rim from the latter. 
I have not met with the genal spines described by Prof. Hartt, 
but the indrawn and upturned genal angle of the head shield 
forcibly recall similar features in more than one species of 
Microdiscus of the Olenellus Zone. 
TRANSACTIONS N, Y. ACAD. Scl., Vol. XV., Sig. 16, Sept. 26, 1896. 
