No. 407.] A SINGULAR ARACHNID. 839 
and Sórensen's paper, this is because I have confirmed nearly 
all of their observations, published in a journal that may not 
be accessible to the reader, and because I am able to adda few 
facts of interest. An account of the internal anatomy, by 
Miss Augusta Rucker and myself, is reserved for future 
publication. 
The observations of Grassi and Hansen and Sorensen refer 
only to the female Koenenia, as the male was quite unknown to 
these investigators. In more than a hundred specimens I find 
only one which may, perhaps, be the male of this arachnid. 
To this I shall return in the sequel, after describing the 
female. 
The general appearance of the female is correctly shown 
in Fig. 1, although in life the first pair of appendages, the 
chelicerze, have their chela bent down so that they are not 
visible from above, and the caudal filament, or flagellum, is 
turned up over the back, or at least carried obliquely upwards. 
The length of the body varies from .7 to 1.25 mm. ; the length 
of the caudal flagellum nearly equals that of the body. The 
animal is of a translucent white color except for the blades 
of the chelicere, which have the yellow tint of thickened 
chitin. The general chitinous integument is very thin and 
transparent, scarcely differing in thickness in the segmental 
and intersegmental, and on the dorsal and ventral regions of. 
the body. The body and limbs are sparsely covered with 
bristles, which have a characteristic arrangement. They are 
delicately plumose under a high magnification. 
The trunk proper consists of the head, thorax, and abdomen. 
The head, comprising at least four segments, as indicated by 
its four pairs of appendages, is covered dorsally with an elon- 
gate octagonal cephalic plate, or shield. This is broadest in 
the region of the coxz of the third pair of limbs. It is 
abruptly declivous in front to the insertions of the chelicere. 
There are no traces of eyes, but Hansen and Sórensen have 
discovered two pairs of minute sense organs “as if in compen- 
sation ” for the lack of visual structures! “The foremost of 
these couples is situated in the median line of the body and on 
1 Loc. cit., pp. 230, 231. 
