MAKINE ISOPOUA OF NEW ENGLAND, ETC. 317 



in length, but the carpus of larger diameter than the propodus ; the 

 iactylus short, cylindrical, and provided with two terminal hooklets. 

 There are a few scattered spinules and setse on the segments, especially 

 the merus, carpus, and propodus. In the males the merus and carpus 

 of the sixth and seventh pairs of legs are provided on their inferior mar- 

 gins with close-set slender curved hairs, which extend nearly the whole 

 length of the carpus and over the distal half of the merus. 



The pleon is proportionally broader and shorter in the male (pi. I r 

 fig. 8) than in the female (pi. I, fig. 7). It is broadly rounded behind^ 

 continuing the outline of the body without break, and is notched 

 at the tip for the insertion of the uropods, which scarcely project 

 beyond the general outline of the body, and consist on each side of 

 a short, stumpy, cylindrical basal segment, a little oblique at the end 

 where it bears two almost rudimentary rami, the inner about twice 

 as large as the outer, and both tipped with a few short sette. The 

 lateral margin of the pleon, like that of the body generally, is beset 

 with short, scattered, unequal seta3 or spinules. Underneath, the pleon 

 is excavated for the branchial pleopods, which are covered and protected 

 below in the females (pi. I, fig. 7) by a large subcircular plate, sparsely 

 minutely ciliated on the margin. In the male (pi. I, fig. 8) the under 

 surface of the pleon presents on each side a small oval plate, with its 

 inner margin overlapped by a median elongated plate, divided by a cen- 

 tral suture, which is open distally. This plate is broad at the base, then 

 narrows toward the middle, after which it expands much more rapidly 

 into an outwardly curved and pointed lobe on each side, ciliated at the 

 tip. Between these two lobes the plate is terminated by two transverse, 

 subquadrate and elongated lobes, which are broadest internally where 

 they are separated along the median line. They are excavated on the 

 anterior margin and less so on the posterior margin, sparsely ciliated 

 behind, and conspicuously so with divergent cilia at the outer short, 

 straight margin. In the females the incubatory pouch appears to be 

 confined to the second, third, and fourth segments. 



In size as well as coloration this species varies greatly, females being 

 often found with eggs when less than half the size of the specimen fig- 

 ured. They attain a length of 5 mm and a breadth of 2 mm , but the males 

 are at least one-third smaller and somewhat narrower than the females, 

 the sides being more nearly parallel. In color there is also much varia- 

 tion. A common color is a dark, slaty gray, with dots or small blotches 

 of yellowish, this color prevailing along the anterior margin of the head. 

 Very frequently darker or lighter shades of green occur, and the incu- 

 batory pouch of the ffemales is often bright green. Some specimens are 

 very light colored or nearly white, often with two or more transverse 

 dark bands, with considerable contrast in color; others are reddish 

 brown throughout. 



I am unable to separate the American form, Jcera copiosa Stimpson, 

 from the common English and European species, although they have 



