THE ANNALS 
MAGAZINE OF NATURAL HISTORY. 
[THIRD SERIES.] 
No. 104. AUGUST 1866. 
XIV.—Memoir on a new Parasitic Crustacean belonging to the 
Order Lernzida, forming a new Family. By M. Hessn*. 
THE object of this memoir is to make known a new Crustacean, 
which, from the simplicity of its structure and the singularity 
of its habits, must, I think, excite the curiosity of naturalists. 
They will judge, from the description we shall give of it, of the 
embarrassment in which we could not but find ourselves, in the 
absence of all definite characters, to assign it a place in the 
classification of organized creatures. 
§ 1. Description. 
It is from 10 to 12 millimetres in length and 2 millims. in 
breadth ; its body, covered with a parchment-like skin, is cylin- 
drical and fusiform. It is essentially retractile in the direction 
of its length; and the segments of its abdomen, in consequence 
of the width of their inferior margin, can even become invagi- 
nated one within the other. It is divided into five thoracic and 
siz abdominal segments. 
Seen from the back, the Aead terminates in a rounded point, 
and presents in the middle a single eye, which, under different 
degrees of incidence of light, exhibits a play of colours varying 
from red to blue. 
The thoracic segments are not very distinct, with the exception 
of the first two, which are easily recognized. The others are 
merely indicated by lateral depressions, especially when this 
part is tumefied by the accumulation of eggs; they increase in 
depth and width as they approach the base: the last, in parti- 
cular, is much larger than the rest, is rounded laterally in the 
middle, and then contracts at its junction with the first abdo- 
minal segment. 
_ ™ Translated by W. S. Dallas, F.L.S., from the ‘ Annales des Sciences 
Naturelles,’ série 5. tome v. pp. 265-279. 
Ann. & Mag. N. Hist. Ser.3. Vol. xvii. 6 
