250 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
KEY TO THE GENUS ALONELLA. 
I. Rostrum long, bent backwards. a aes ik ea ease Palla setae a es 
II. Rostrum short. 
A. Lower posterior angle toothed. 
a. Shell more or less reticulate. 
* Reticulated areas minutely striate. pulchella, 250; excisa, 251 
** Reticulated areas smooth. 
+ Flead:depressed. 2). Se tie eee 2 IST eos 
{+t Head horizontal. . =. . : - . grisea, 252 
b. Shell marked by lines running aiaeoncilly ipaatd and 
backward, *..2 3-5). .- . . pygmeea, 253 
B. Lower posterior angle aritpobie sell ier etteeiaralig striate. sStriata, 253 
Alonella rostrata Koch. 
Lynceus rostratus—Koch, Lilljeborg, Schoedler. 
Alona rostrata—P. E. Mueller. 
Pleuroxus acutirostris—Birge. 
Pleuroxus affinis—Herrick. 
Body long, rapidly narrowed behind; dorsal line strongly arched 
in front toward the depressed head; the lower margin straight, with 
0-3 small teeth at the angle. The fornices are broad, but the beak 
is sharp; the pigment fleck is but little smaller than the eye, to which 
it is three times nearer than to the beak. The post-abdomen is long, 
very much as in A. excisa, but longer. Length 0.4 to 0.5 mm. 
Schoedler says the lower margin is concave and the angle unarmed, 
a condition not inconsistent with specific identity, as can be seen in 
many other species. The shell seems to be variably marked, but most 
conspicuous are the diagonal, curved strize. Schoedler compares the 
sculpture to P. exiguus; Kurz, however, leaves the impression that 
only slight reticulation is present in the female. 
The male has the post abdomen narrowed, ornamented with 
clusters of hairs behind, and the small claws have no basal spine, 
while the genital opening is in front of the claws. 
* Alonella pulechella Herrick. 
PLATE XIII, Fics. 1-3. 
A minute form very recently obtained is described under the above 
name. Although closely allied to A. evigua, this species is more like 
Graptoleberis than any other member of the genus. It is the smallest 
of the Lynceids, excepting A. pygmea. The shell is high and rather 
strongly arched; the posterior margin is short and armed with four 
teeth below, wiih point in different directions as in Graptoleberis. 
The head is short and the antennules long. The pigment fleck is of 
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