1896. | NEW YORK ACADEMY OF SCIENCES. 207 
Sculpture.—All these forms of plates, except for the keels and 
furrows described, have a comparatively smooth surface, there 
being only obscure lines of growth, and these not usually seen 
except toward the edges of the plates, and to these edges the 
lines are parallel. 
Horizon and Locality.—Gray shales of Div. 1 ¢ at St. John 
and Hanford Brook, St. Martin’s. Somewhat rare. 
The reference of these plates to Cirripedes is largely a matter 
of conjecture. As oval and circular plates have been found to 
occur along the dorsum of several genera of fossil Cirripedes 
plates of the type L and D may have had such a position, those 
of type B are evidently lateral, though the elongated form is 
unusual. Plates of the type Care more plentiful than the others 
and have the appearance of overlapping lateral plates. I have 
seen plates from the crown and lateral edges of a Trochocystites 
that resemble these, with similar flange and furrow. Plates of the 
type £ more nearly resemble the opercular armature of modern 
Cirripedes, and seem to be the representatives in the old rocks of 
the conical plates of Plumulites,* and are perhaps scutal plates, 
while the type @ is analagous to the laterals of such a genus as 
Sealpellum.+ The longitudinal curved ridge of type Ff’ is com- 
parable to those figured by Barrande. Hall and J. M. Clarke.{ 
The broad sub-semicircular or subtrapezohedral form of many 
of these plates may seem unusual, but is not without a prece- 
dent in extinct genera, as Archzolepas and Loricula, which have 
rows of similar broad plates on the peduncle.§ 
In the shales which contain Plumulites Manuelensis at Man- 
uel Brook, Newfoundland, are casts of calcareous plates which 
are similar to the above, thus resembling the coronal plates of 
‘Trochocystites ; but they are different in form from those of the 
Eteminicus zone at St. John; the commonest form has a very 
heavy keel or furrow and is truncated at each end. ‘The mate- 
rial is insufficient to determine the nature of these plates, which 
are sparsely scattered over layers in which Microdiscus punc- 
tatus abounds. 
TRILOBITA. 
AGnostus, Brongniart. 
This is the most aberrant of all the primordeal trilobites of 
common occurrence, and the most difficult to associate with the 
*Syst. Silur. Bohem., vol. i., Supp. pl. 20, figs. 7,8 and9 6. Pal. N. York, vol. vii., 
pl. xxxvi., figs. 1 and 3. 
+Traité de Paleontologie, Zittel & Barrois, tome ii., p. 536. 
tSyst. Silur. Bohem. vol. i., Supp. pl. 20, figs. 22, 1 a and 5b; also Pal. N. Y., vol. 
vii., pl. xxxvi., figs. 10, 11 and 16. 
2 Traité de Palzeontologie, Zittel and Barrois, p. 533 and 534. 
