of the Pacific Shores of North America. 478 
The superior surface of the carapax is raised into a. high 
ridge along the median line, deeply sinuated between the 
stomachal and cardiac regions, the former of which is a little 
shorter and less prominent than the latter. The branchial 
regions are rather small, and much less prominent than the 
cardiac. The intestinal is continuous with the cardiac pos- 
teriorly. The wings or lateral portions of the shield are 
broadly expanded, subtriangular ; their extremities covering 
the terminal joints of the third pair of feet extended. The 
surface is rugose at the prominent parts, but generally 
smoothish and ungranulated, although discolored and hav- 
ing a somewhat eroded appearance. The rostrum is lamel- 
liform, rectangular, pointing downwards at an angle of 
about 60? with the horizontal axis —its truncate extremity 
is still more deflected and slightly emarginate at the 
middle. 
The arrangement of the eyes, antenne, and other parts in 
the vicinity of the mouth, is generally similar to what we 
see in Echidnocerus and other genera of the family. The 
ocular peduncles are closely approximated at their base, and 
are rather long, allowing the eyes at their tips to be seen 
from above in the angle between the base of the rostrum 
and the anterior margin of the carapax, which constitutes 
the only vestige of an orbit. The internal antenne are 
slender, inserted behind the base of the ocular peduncles, 
and much within the margin of the carapax; they are 
directed forward between the eyes, and terminate in a slen- 
der, hairy, multiarticulate flagellum, longer than the penul- 
timate article, and not reaching the extremity of the ros- 
trum. The external antenne occupy the hiatus between 
the anterior margin of the almost vertical pterygostomian 
Plates, and the exterior bases of the internal antenne. Their 
Second article is broadly expanded, and bears a lamelliform 
appendix which equals it in size, projecting much beyond it 
exteriorly, and reaching the margin of the carapax ; both 
are of large size, and bear short, blunt hairs on their lower 
JOURNAL B. s, N. H, 61 
