342 
Psyche 
[September-December 
(1946) gave a key for species known from the Canal Zone and 
adjoining regions. 
Distribution has been discussed by many, including Brinck (1956), 
Brues (1923) and Clark (1913a, 1913b, 1915a, b). The circum- 
tropical distribution of the family Peripatidae and the generally 
south temperate distribution of the family Peripatopsidae have led 
several authors to speculate that these distributions have been 
achieved through a Gondwana. or continental drift mechanism (for 
instance, Cuenot, 1949; Hutchinson, 1928). However, although 
continental drift may be a fact, onychophoran distributions have not 
necessarily been controlled by it alone, and active, dynamic biological 
factors were probably more important in forming the distributions 
(Brinck, 1956; Darlington, 1965). 
Since the summary papers by Bouvier and Clark, several species 
have been described and others have been placed in synonymy. The 
following key to the genera and list of species unites this dispersed 
literature and hopefully will provide a basis for encouraging further 
studies. 
Key to the families and genera of New World onychophorans 
1 a. Sexual opening between last pair of legs (Fig. 1); Peripatop- 
sidae, Peripatoidinae ; south-temperate distribution in southern 
and central Chile Metaperipatus 
ib. Sexual opening between penultimate pair of legs (Fig. 2) ; 
Peripatidae, Peripatinae. 2 
2a. Nephridial tubercles (urinary papillae) of fourth and fifth legs 
indenting proximal margin of third creeping pad band on leg, 
usually dividing third pad into two segments (Fig. 3); four 
or five creeping pads; four foot papillae, 2 on each side of 
foot. Oroperipatus 
2b. Not the above combination; nephridial tubercles of fourth and 
fifth legs perhaps connected to third pad and indenting its prox- 
imal margin, but opening in space between third and fourth 
creeping pads, usually indenting fourth pad or rarely dividing 
fourth pad into two segments (Figs. 4, 7) ; usually four (rarely 
five or three) creeping pads (Fig. 4) ; three or four foot papil- 
lae 3 
3a. Four foot papillae (three anterior and one posterior, or rarely 
two anterior and two posterior) (Fig. 4) ; El Salvador. 
Ileteroperipatus 
3b. Three foot papillae (two anterior and one posterior, Fig. 7). .. 4 
