of the Pacific Shores of North America. 473 



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, antennae, 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 antennae 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 antennae occupy the hiatus between 

 the anterior margin of the almost vertical pterygostomian 

 plates, and the exterior bases of the internal antennae. 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 



