208 Dr. David Sharp on 
is a little coarser on the apical than it is on the basal 
part. The female differs but little from the worker. 
Myroicipes.—Pseudomyrma, sp. (worker). Guatemala. 
The lines in this species are excessively fine, but the 
structure in other respects appears similar to Sima rufo- 
nigra. In working with a specimen of this species taken 
from spirit, I detected an excessively minute sound when 
the appropriate movements were made. 
Myrauiciprs.—Gen. ?, sp. (female). Amazons. The 
segment behind the second node forms on the dorsal 
aspect a well-marked scutellum; its surface is very 
peculiar, the outer layer of the integument being colour- 
less and transparent, so that the structure and colour of 
the inner layer are seen through the outer one, and 
render the external condition of this latter very difficult 
to distinguish. It appears, however, that at the sides 
there is a rough irregular but very fine sculpture, and 
in the middle a broad oval space, which is very finely 
and regularly striate. I think the lines in this insect 
are finer and closer than in almost any other; the length 
of the exposed part of the scutellum is about five-eighths 
of a millimetre, and, as a rough estimate, I should say 
there are nearly 200 lines on it, which would be at the 
scale of 7000 or 8000 to the inch. Fig. 6. 
The perfect transparency of the stridulating surface in 
this species is very remarkable ; the inferior layer of the 
derm can be seen through the outer, even at the sides 
of the neck, but the outer surface, on which the lines 
are situated, is quite transparent, and the layer beneath 
seems to be of cellular structure. The conditions seem 
to indicate that this part of the skeleton may be more 
resonant or give a purer note than ordinary chitine 
would. 
MyrmicipEs.— Atta cephalotes (worker major). Amazon 
Valley. (Undissected specimen). The portion that can 
be exposed of the neck of the segment following the 
second node is not extensive, and is quite dull, owing to 
being covered with densely placed transverse but some- 
what irregular and interrupted lines; along the middle 
there is a slightly raised space, and this is covered with 
quite regular, much coarser, and more sharply elevated 
lines; the surface of the neck of the segment is very 
strongly curved, the convexity being in two directions, 
as in a convex lens. 
