, 
416 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM: 
either side, between the branchial region and the posterior part of the 
gastric and the cardiae region, and with the surface rough and tuber- 
culose. The cardiac, with the posterior part of the gastric region, is 
raised into a continuous ridge, capped with a longitudinal line of four 
large spiniform tubercles, one on the gastric and three on the cardiac, 
besides a-small one in the middle of the posterior margin. The cardiae 
and the two anterior gastric tubercles are erect and their tips nearly in 
the same horizontal line, while the posterior cardiac is’ situated much 
lower down on the posterior slope of the carapax and is direeted upward: 
and backward. In front of the gastrie tubercle there are two much 
smaller ones, in a transverse line, and in front of these there are usually 
four still smaller ones similarly disposed, so as to make a submedian 
line of three small tubercles either side, between the large gastric tubercle 
and the erect and prominent tubercle upon the crest of the orbital arch. 
Jn one of the specimens the most anterior of these three pairs of tubercles 
back of the orbits is obsolete. There is a deep longitudinal depression 
between the orbits, and extending a little back of them and forward to 
the narrow part of the rostrum. The rostrum is prominent, directed 
forward and downward, suddenly contracted just in front of the antennal 
fosse, leaving a dentiform tubercle either side, where the rostrum is 
suddenly narrowed; there is also a small tooth either side, near the tip 
of the rostrum. The antero-lateral margin. is strongly ineurved at 
the cervical suture, so as to approach closely and expose slightly from 
above the strongly tuberculo-dentate, infero-lateral carina, which is itself 
slightly ineurved at this point; both in front of and behind the cervical: 
suture, however, the margin reeedes from the inferior carina, in front 
being directed upward at an oblique angle with the part behind the 
cervical suture. Above this angle there is a broad, conspicuous, and 
nearly smooth depression in the nearly vertical surface. The margin 
between the cervical suture and the orbit is armed with two small tuber: 
cles near the cervical suture, but the anterior two-thirds is unarmed and 
slightly concave in outline. Behind the cervical suture the margin is 
regularly and very strongly arcuate, and in front of the great branchial 
tooth, which really forms the lateral angle of the carapax, is armed with 
nine or ten teeth, of which the first three or four are small and some- 
what tuberculiform ; the six posterior are larger, acutely triangular, and 
strongly laciniated, the four anterior of these six being nearly equal in 
size, the fifth larger and the sixth smaller than the others. The greatest 
breadth of the carapax is between the tips of the large fifth laciniated 
tooth each side, or, excluding the teeth, between the bases of the third 
and fourth teeth each side. The great branchial tooth is larger than 
any other, laciniated, and has a small tooth at the base in front and a 
larger one near the base behind; and still behind this last there is first 
a small and then a much larger tuberculiform spine on the concave 
postero-lateral margin, while the short posterior margin is armed with 
three prominent tubercles, with several smaller ones between. The 
