ACADEMY OF SCIENCES. 45 



small claws, and the three anterior pairs sub-dactyle, as in Pterelas in the fam- 

 ily jEgidm. 



Idotaga longicauda. 



Thorax increasing in width to the central segment, length of segments 

 nearly equal, the posterior slightly shorter. Cephalic shield deeply emargin- 

 ated at sides, each border forming two blunt "teeth. Epimera large, pointed, 

 extending behind their respective segments, the backward curvature increas- 

 ing with each successive segment. Abdomen at origin as wide as thorax, first 

 three segments pointed on each side, the point directed backwards; fourth 

 segment narrower and shorter than the others, and enclosed laterally by the 

 third; terminal segment very long, more than one-third the total length of 

 animal, and gradually diminishing to a truncate point. 



Eyes remote, inconspicuous. Flagellum of external antenna? nine-jointed. 

 First joint very long, flagellum about equal in length to base, which is hirsute 

 on interior margin. Internal antennae reaching to near middle of ultimate 

 basal joint of outer antennae. Fiist three pairs of legs sub-didactyle, with a 

 short hatchet-shaped process on the joint preceding the manus, which is 

 broad and margined with short hairs on palmar border. Four posterior pairs 

 of legs with short stiff hairs on the upper margin of 3d, 4th, and 5th joints. 



Two specimens showing a slight difference in the form of the caudal seg- 

 ment, which in the smaller specimen has an obtuse angle on each lateral 

 margin, at about one-third of its length from the extremity. 



Length of large specimen, 2.80 in.; greatest breadth across epimera, 1.00 in. 



Length of smaller specimen, 1.80 in ; greatest breadth, 0.66. 



The larger one was found by Capt. T. W. AVilliams, in lat. 67.30 N., long. 

 163.02 W., near tbe coast of Alaska. The smaller specimen was found by 

 J. W. Fisher. 



The larger is a skeleton only, the smaller, a male, in alcohol. 



This species is totally distinct from any yet found on the Pacific Coast, but, 

 since it occurs so far to the north, it is possible that it may b| identical with 

 some previously described species from the Arctic waters of the northeast of 

 America. 



Sphazroma olivacea. 



Cephalic shield curved anteriorly, distinct from the first thoracic segment, 

 which is but slightly longer than either of the succeeding four segments; last 

 two thoracic segments very short. Abdomen with two distinct joints, the 

 first marked with two partial sutures; the hinder segment curved posteriorly; 

 caudal process not reaching beyond the caudal segment. 



Length, % of an inch. 



This species is exceedingly common in the lagoons of the salt-marshes at 

 Fort Point, San Francisco, where it resides among weeds, or adhering to the 

 underside of sticks, etc. 



The chief distinctions between this species and S\ Oregonensis as figured by 

 Dana, are the more projecting cephalic segment, and the small size of the 

 two hinder thoracic segments. 



