RHACHODESMIN. 171 
Key to the Central-American Genera. 
a. All the pores absent, except a single pair upon the fifth segment. . . . Dvoporus. 
a’. Pores retained upon other segments, normal in number or in excess of 
the normal. 
6. Pores abnormal in number, present upon segments 8, 11, and 14. . . SrroneyLopEsMus. 
6. Pores normal in number, absent upon segments 8, 11, and 14. 
c. Distal segment of phallopod bent at a right angle to the coxa and 
bearing a distinct seminal fossa at the base on the inner side. 
d. Seminal fossa of phallopod forming a circular or subcircular pit 
lined with hairs. 
e. Keels elevated, spiniform, with acutely-pointed angles . . . . RuacHrIpoMoRPHA. 
e’. Keels broad, laminate, not spiniform. 
f. Lateral edges of keels scarcely thickened, but markedly irre- 
gularin outline . . . . RHACHODESMUS. 
jf’. Lateral edges of keels markedly thickened, with evenly rounded 
outline . 2. 2. 1. we. Loe . . . . . PARARHACHISTES. 
d', Seminal fossa of phallopod not closed on its distal side, but opening 
into a wide channel traversing the inner surface of the segment. 
g. Keels small, ending posteriorly in a sharp tooth; phallopod 
3-pronged, the seminal stile narrow acuminate, not longer 
than the auxiliary branches . . . . 1...) . . s) .) . )06ACUTANGULUS. 
g'. Keels large, not markedly spiniform; seminal stile of phallopod 
compressed, sublaminate, and much longer than the auxiliary 
branches . . . woe 6 6 «© + ee). )6NEOLEPTODESMUS. 
. Distal segment of phallopod not bent at a right angle to the coxa, 
the two segments axially in the same straight line and protruding 
vertically from their socket ; no distinct seminal fossa at the base 
of the distal segment. 
h. Phallopods large; their sockets large and abutting against the basal 
segments of the legs of the seventh segment; the tracheal rods 
short; anal sternal plate distinctly triangular; keels large and 
overlapping . . . . toe ee soe ee . ACERATOPHALLUS. 
h*. Phallopods very small with long and cylindrical tracheal rods : ; 
their sockets very small and remote from the basal segments of 
the legs of the seventh segment ; anal sternal plate semi-oval. 
i. Keels medium-sized, not overlapping; sternal areas not com- 
pressed and bituberculate behind; legs with sixth segment 
much longer than fifth. . . . . oe . . . «+ « PAMMICROPHALLUS. 
. Keels very large, wide, overlapping and depressed ; sternal areas 
narrowed posteriorly, with their posterior border deeply angled 
and bidentate ; legs with sixth segment only a little longer 
than fifth . . . 2. 2. 2. ee ee eee ee 6. )6ZEUCTODESMUS. 
Z2 
