JERA NORDMANNI. 821 
ingly removed it therefrom, and formed for its reception 
a new genus, Jeridina, in consequence of the branchial 
apparatus on the underside of the tail not being covered 
by a ‘‘ grande lame operculaire qui chez eux remplace les 
premiéres fausses pates” (which had been given as the 
generic distinction between Asellus and Jera). Having, 
however, ascertained that this ‘‘ grande lame” is a sexual 
distinction peculiar to the females, we are under the 
necessity of referring the new species to the genus Jera, 
with which it agrees in all its essential characters. 
It is considerably broader than J. albifrous, the lateral 
margins being very thin and dilated, as well as ciliated 
with rather strong bristles set on at right angles, a 
peculiarity of structure eminently fitted for enabling the 
animal to reside in flat crevices, beneath stones, &c., in 
situations often uncovered by the tide; the ciliation of 
the sides of the body serving for the retention of the 
fluid which supplies the material for respiration; just 
as in many insects residing in occasionally submerged 
situations under stones, it maintains a supply of air for 
the like purpose. The head is deeply incised in front, 
for the reception of the antenne, the inner pair of 
which are very short, and four-jointed, the terminal joint 
offering no apparent trace of articulation; the outer 
antenne are not more than one-third of the length of 
the animal, the third joint being only about twice the 
length of the preceding, and not half as long as the 
following joints, the flagellum is very slender and multi- 
articulate. The terminal segment, or tail, is large and 
semicircular, with a rather deep semicircular incision 
at its extremity, within which are affixed the two caudal 
appendages, consisting of a small oblong basal joint, at 
the extremity of which are attached two small scales, 
the outer one being extremely minute and conical, the 
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