1896. | NEW YORK ACADEMY OF SCIENCES. 195 
Valves obliquely semi-elliptical, about one-third longer than 
wide; hinge line straight, umbo less than one-third from the 
front of the valve. Tumid part of the valve occupying about 
one-third of its length and about one-half of its width; valve 
flattened toward the anterior and posterior ends. A faint nar- 
row rim is traceable around the outer edge of the valves. 
The cast of the right valve has a triangular umbonal promi- 
nence, about one-third from the front; the prominence is lim- 
ited in front by a sharp and deep furrow, placed at right angles 
to the hinge line, and extending thence toward the base of the 
valve; the umbonal elevation is somewhat hollow in the middle, 
where it bears a sharp, narrow ridge, which is directed toward 
the posterior margin, at an angle of 50° from the hinge line; a 
faint furrow connects this ridge with the point of the umbo. 
The outer surface of the valves of this species is marked by 
numerous concentric striz, and by two faint radiating furrows, 
extending on each side of the tumid part of the valve to the 
basal margin. 
The sharp median ridge and connected furrow, seen in the 
cast of the right valve of this species, are similar to those on the 
dorsal valves of some Brachiopods, but the position of the umbo 
separates it from that class of molluscs. 
Length, 1 mm. Width, ? mm. 
Horizon and Locality. In the fine, gray shales of Div. 1. ¢, 
at Hanford Brook, St: Martin’s. Infrequent. 
LEPIDITTA CURTA (Plate XV., fig. 2). 
Lepiditta curta, Trans. Roy. Soc. Can., Vol. IIL., pt. iv., p. 
Gi opl. vi., fio. LT. 
Obliquely semi-elliptical and about two-sevenths longer than 
wide ; hinge line nearly straight ; umbo depressed, less than one 
quarter from the front of the valve. Valves flattened toward 
the base and posterior end, the anterior margin has a flattened, 
depressed rim; and the front of the rim in the two valves was 
apparently connected by a triangular piece not bounded by dis- 
tinct sutures. 
The interior of shell has roughened zones or undulations con- 
centric to the umbo. 
This organism is not unlike the crustaceans of the genus 
Estheria, but its resemblance to the preceding spevies, in form 
and hinge characters, indicates a generic relation. 
Length, 14mm. Width, 14 mm. 
Horizon and Locality. In the fine dark shales of Div. 1.d!, 
at Porter’s Brook, St. Martin’s. Rare. 
