384 THE AMERICAN NATURALIST. | [Vor. XXXIX. 
shows them. The variation in the central markings is shown 
in the two figures. In certain specimens examined the two 
sides of the same specimen varied much from each other. 
As a whole the carapace is quadrangular, considerably broader 
in front than behind. The front angles have four teeth as 
described by Dr. Stimpson. Three of these are large, the first, 
second, and fourth, while. the third is decidedly smaller. The 
orbits, as described, occupy about one third the breadth of the 
front of the carapace. The border is entire and raised, and is 
composed of crowded granules. 
The front is nearly one fourth the width of the carapace and 
has a somewhat different form from that figured by Dr. Stimp- 
son as a comparison of the figures will show. Excellent speci- 
mens of this part were obtained showing the complete form. 
There are two lateral lobes on the anterior border and a median 
lobe which is cut on the median line, making it emarginate. 
The front as a whole is bent downwards as shown in Pl. rn Fig. 
I. In the restoration it is drawn as though slightly raised to 
give its true shape (Pl. ı, Fir. 
In the specimens broken from large concretions the eyes 
have very frequently been excellently preserved. They have a 
prominent basal joint, with an expanded cylindrical outer portion 
of the shape shown in the figure. It seems strange that Dr. 
Stimpson did not obtain good specimens of the eyes for they : 
have appeared very frequently in the collections of the last two 
summers. 
Of the antennz little was made out except their position 
which is but very slightly anterior to the base of the eyes. 
The bases of the antennze appear as cross sections and as small 
bits now and then. 
One specimen (Pl. 2, Fig. 5), showed the pair of antennules 
extending slightly beyond the front, but here again it was impos- 
sible to make out much more than their presence and position. 
Turning to the ventral side, almost the entire features bave 
now been made out and are included in the synthetic figure (Pl. 
2, Fig. 6). The sternum is excellently preserved in a consider- 
able number of specimens. A cast from the white layer showing 
all the minute tubercles was obtained (B. S. N. H. no. 12,977). 
