170 
[OCTOBEB 
B, ARIDA Say (Walsh.) There is nothing in Say’s brief descrip¬ 
tion which opposes the identity of B. arida Walsh and Say. The 
words “ anterior tibiae whitish obscure at base and tip,” were a little 
suspected by me, but I see that in reality the % (Walsh) has the 
tibiae a little pale. Two % % received from Mr. Walsh in 1860, 
one of which is much smaller than the other, have the tibiae altogether 
black. See note The “orbit” is, according to Say’s Grlossary, 
“ an imaginary border around the eye.” “ Vertex with a small black 
spot each side on the orbit,” agrees very well with the 9 , but the tibiae 
of the 9 are all black. I cannot find the 9 from Washington (cited 
Syn. p. 46), but after a careful revision of my other Ephemerina, I 
find I have not received this species except from Mr. Walsh. 
B. SICCA Walsh. A good species. “ Abdomen piceous above ex¬ 
cept the last segmentI can see no dififerent color, or even different 
shade of color, in the last segment. \_See note 9.] It seems to me 
that the base of the first joint of the anterior tarsi is black. [>S^ec note 
10.] I have received a S of this species from Washington, and in 
1860 I also received from Mr. Walsh, along with a small specimen 
of the % 9 imago, a % subimago, which probably belongs to this spe¬ 
cies. The character of the [anterior] legs being short in the % is a 
good one, and so is that of the brown incisures of the setm; but in any 
case it seems to me that a more precise comparative description, with 
indications of differences, would still be desirable. \_See note 11.] 
The % from Washington, for example, is partly intermediate between 
arida and sicca^ for the setae have only some dark incisures at their 
base. In S S of the genus Baetis, sometimes the form of the penis is 
a very good and easily seen character, but I cannot get to see this or¬ 
gan in these two species. Possibly it can be more easily done in the 
living specimens. After all, I am convinced that these are two diffe¬ 
rent species. 
B. DEBiLis Walsh. I only know the pair received from Mr. Walsh. 
The diagnosis of Walker is too brief, but it contains nothing contra¬ 
dictory. The S has the penis bifid, black, the two bifurcations straight 
and parallel, a little tapering towards the tip. This character is very 
easily seen, because the color of the apical parts of the abdomen is 
altogether pale. 
B. ALBA Say. There is an Article by Dr Williamson, “ on the 
