04 NEW YORK STATE MUSEUM 
on each side, the middle one is inverted in position, the apex point- 
ing outward (downward). Carina and rostrum little different in 
size from each other and from the lateralia. Compartments fused 
only near the base. Terga and scuta not known. 
Genotype: Eobalanus informans nov. 
Eobalanus informans nov. 
Plate 1 — figs. 1, 2; plate 2, figs. 1, 2 
Description. Wall elliptic or oval in outline, the major and 
minor diameters to each other as 4:3; consisting of 12 free plates 
(termed compartments): 5 symmetric lateralia, and the asymmetric 
carina and rostrum. Scuta and terga have not been observed. The 
lateralia are wedge-shaped but so arranged that they interlock, the 
outer pairs being broadest at the base (outside), the next pair also 
narrowing toward the top but with the apex truncated, the middle 
pair, however, widest at the top, thus forming a sort of keystone 
in the series of plates. One of the asymmetric plates is somewhat 
larger than the other, this end of the wall having been apparently 
-more acute than the other, producing an oval outline. These wall 
plates were inserted in an elliptic base, the impression of which 
projects slightly beyond the basal edges of the wall-plates. 
The surface of the compartments is smooth; save the growth-lines 
that run parallel to the basal margins. 
Measurements: The largest specimen observed measures 28 mm 
in length and 23 mm in width; a smaller complete specimen is 9 mm 
long and 7 mm wide. 
Horizon and locality. All specimens observed were attached to 
the conchs of Geisonoceras, mainly G. amplicameratum, 
from the Utica shale at Holland Patent. 
Eobalanus trentonensis nov. 
Plate 1, fig. 3; plate 2, fig. 3. 
This species is based on a single imperfect specimen, which rep- 
resents an extremely rare fossil, for in a thorough search of the 
large Rust collection of Trenton cephalopods we obtained but this 
meagre result. It is of great interest as another, still older, repre- 
sentative of the genus Eobalanus of primitive acorn barnacles. 
The specimen exhibits the lateralia of only one side distinctly while 
those of the other side which became fossilized in their original 
upright position, are more or less foreshortened. The carina and 
