78 
Psyche 
[March 
American Museum of Natural History together with Dr. G. Owen 
Evans and Mr. D. J. Clark, Dept, of Zoology, British Museum 
(Natural History) for the loan of valuable specimens. 
Genus Ischnothyreus Simon, 1893 
The type species is Ischnothyreus peltifer (Simon) by monotypy. 
The genus was established on the basis of a female from St. Vincent, 
B. W. I. and placed in the genus Ischnaspis, 1891. Simon soon found 
that this name was preoccupied and he then changed the name of the 
genus to Ischnothyreus in 1893. As a result of my study of the species 
treated in this paper I think the most important features of the 
genus may be stated as follows : The total length varies from nearly 
1.25 mm in males to about 2.25 mm in females. The body and ap- 
pendages are only moderately chitinized with the exception of the 
male palps in contrast to such genera as Dysderina , Opopaea and 
Scaphiella. Carapace moderately tall; about three fourths to four 
fifths as wide as long; thoracic region well rounded along ventral 
border; much narrowed just behind PE; without any median groove 
or pit. Sternum more or les scutiform; quite convex; surface smooth 
with a moderately developed coat of hair; extended between bases 
of fourth coxae which are separated by at least their width and 
usually more than this. Eyes : six in two rows, in a compact group ; 
AME lacking; ALE either almost in contact medially or narrowly 
separated; eyes of posterior row close together; posterior row either 
straight or slightly procurved, viewed from above (Fig. 1 and Fig. 2, 
Suman, 1965); with no marked size differences. Legs: 4123 in 
order of length; moderately long and slender; first two pairs with 
more or less conspicuous, long, ventral spines on femora, tibiae and 
metatarsi; trichobothria present on at least tibiae and metatarsi and 
on certain segments of the palps; apparently, third and fourth legs 
without true spines. In females the chelicerae are simple and without 
special modifications. In at least two species (/. peltifer (Simon) 
and I. omus Suman) the males have a curious knob or hook at the 
base of the fang (Figs. 2-3) ; the fang groove appears to have minute 
teeth along the margins in at least certain species (Suman, 1965, 
Fig. 4). The lip is simple, without special modifications. The max- 
illae are simple and unmodified in females but in males of certain 
species they are distally modified (/. peltifer (Simon), /. indressus 
sp. nov.). The palp in females is also simple and without special 
modifications but in males it has a more or less distinctively modified 
tarsus (Figs. 6-8) with other segments simple and unmodified except 
for the strong chitinization and dark brown color in contrast to the 
