1968] 
Chickering — Genus Ischnothyreus 
83 
parative Zoology from Bermuda (N. A. Weber, no date) but has 
never been described. I did not collect this species on St. Kitts. Nevis 
or Virgin Gorda during my visit to these islands in the summer of 
1966. 
Ischnothyreus browni sp. nov. 
Figures 11-12 
Holotype. The male holotype is believed to have been collected 
by Dr. W. L. Brown, Cornell University, in Costa Rica, Rio Toro 
Amarillo near Guapiles, Heredia, March 1966. The species is 
named after the collector. 
Description. Total length 1.23 mm. Carapace .68 mm long; 
.55 mm wide opposite second coxae where it is widest; about .37 mm 
tall; evenly arched from PE to beginning of moderately steep pos- 
terior declivity; smoothly rounded along ventral margin. Eyes: six 
in two rows in a compact group ( Fig. 1 1 ) ; Posterior row wider 
than anterior row in ratio of about 16 : 13; viewed from above, 
posterior row slightly procurved but almost straight. Ratio of eyes 
ALE : PME : PLE = 7.5 : 6 : 6. ALE separated by a line; 
contiguous to PLE at one point; PME contiguous for about one 
fourth of their circumference and contiguous to PLE for a shorter 
distance. Clypeus a little higher than radius of ALE. Chelicerae 
do not have the knobbed fang as in I. peltifer (Simon). Maxillae 
appear to be essentially like those in I. peltifer (Simon). Lip appears 
to be simple and without special modifications. Fragility of the two 
males available prevents the desired close examination. Sternum quite 
convex; only a little longer than wide; bluntily rounded between 
bases of fourth coxae which are separated by 1.3 times their width. 
Legs: 4123 in order of length; spines on certain segments difficult 
to observe but apparently they closely resemble those on the legs of 
I. peltifer (Simon). Palp: general features typical of males of the 
genus; all segments except tarsus short and unmodified except for the 
strong chitinization ; distinctive features of tarsus shown in Figure 12. 
Abdomen: apparently also typical of males of the genus except for 
the scuta which are hardly discernible with borders very indefinite; 
dorsal scutum appears to reach only a. little more than half way from 
base to posterior end; genital aperture very obscure but apparently 
as in the two other species treated in this paper. Color in alcohol: 
carapace yellowish with the relatively large, oval spots, represented in 
figures of I. omus Suman, 1965 from Hawaii, darkest; ocular area 
with considerable black pigment, some of it in front irregularly dis- 
tributed (Fig. 11). Sternum, legs and all mouth parts except palps 
