102 BRISTLE-TAILS AND SPRING-TAILS. 
genera (Orchesella, Tomocerus, and Achorutes, and allied genera), 
but Lubbock was unable to detect them, and I may add that I 
have not found them either in living specimens, or those rendered 
transparent by potash, though careful search was made for them. 
Having given a hasty sketch of the external aspect of the Po- 
duras, I extract from Lubbock a synopsis of the families and 
genera for ‘the convenience of the student, with the names of 
known American species, or indications of undescribed native 
forms. 
SMYNTHURID#. 
Body globular or ovoid; thorax and abdomen forming one 
mass; head vertical or inclined; antenne of four or eight seg- 
ments. Eyes eight on each side, on the top of the head. Legs 
Fig. 26, long and slender, Saltatory appendage with a sup- 
plementary segment. 
Smynthurus Latreille. Antenne four-jointed, bent 
at the insertion of the fourth, which is nearly as long 
as the other three, and appears to consist of many 
small segments. No conspicuous dorsal tubercles. 
(In this country Fitch has described five species: S. 
arvalis, elegans, hortensis, Noveborucensis, and sig- 
nifer. Fig. 26 represents a species found in Maine.) 
Dicyrtoma Bourlet. Antenne eight-jointed, five 
before, three after the bend. Two dorsal tubercles on the ab- 
n. 
i Smynthurus. 
Papirius Lubbock. * Antennæ four-jointed, without a well- 
marked elbow, and with a short terminal segment offering the 
appearance of being many-jointed. 
PODURIDÆ. 
This family comprises those species of the old genus Podura, in 
which the mouth has mandibles [also maxillæ and a labium], and 
the body is elongated, with a more or less developed saltatory ap- . 
pendage at the posterior extremity. í 
Orchesella Templeton. Segments of the body unequal in 51zê, 
*Lubbock considers that Papirius should be placed in a distinct family ee 
Smynthurus, because i wants trachesw. Their presence or absence searcely me al 
us to be a family character, as they'are wanting in the Poduridæ, and are not one 
to the life of these animals, while in other respects Papirius differs but slightly 
Smynthurus. 
heey 
