50 
W. E. PURCELL. 
spines {-spi., fig. 23 a), while near its blind dorsal end it is 
vvitlionb any spines (ec. t. 8, fig. 23 a). 
The hypodermis of the blind end is of special interest. 
Its cells assume a fibrous structure fig. 23) and are not 
pigmented like the adjacent hypodermis, and the large ento- 
chondrite {t. 8) is firmly attached to their basal ends. 
The numerons and powerful muscles which are attached to 
this entochondrite have been described by Schimkewitsch 
(’84), Vog’t (’89), A. Schneider (’92), and others. It cor- 
responds to the anterior of the three pairs of abdominal ento- 
chondrites described by these authors. 
In females of Attus floricola, at any rate in matured or 
nearly matured specimens, the interpul rnonary fold differs in 
a very remarkable manner from that just described. Instead 
of the cylindi-ical spinous canal of communication one finds a 
broad, thin-walled, much wrinkled, band-shaped canal, with- 
out spines inteimally, and strongly compressed from before 
and behind {can., fig. 22). Moreover, the two walls of the 
fold itself, apart from the canal, are much more strongly 
wrinkled than is the case in the male. 
In the adults of both sexes the opening of the genital 
organs is found on the anterior wall of the medial reg’ion of 
the fold between the pair of entapophyses {g. o., figs. 20 and 
23b). 
The interpulmonary fold in other spiders. — The interpnl- 
monary fold ^ was found in all Dipneumonous spiders 
examined by me, and in the majority of the genera resembled 
the conditions occurring in either the male or the female 
of Attns floricola (Marpissa $, Clubiona $, Age- 
lena ?, Pisaura ?, Dolomedes 2, Melanophorad' ? , 
Drassodes ?, Zora 2, Linyphia 2, etc.). 
’Phe pair of entapophyses are very variable in shape, even 
in the same species ; thus out of five specimens of Tegenaria 
domestica (fig. 21) examined, no two had the entapophyses 
shaped exactly alike. In some forms these tendons may be 
‘ This fold was known to Treviranns (T2), and is descriljed Ly 
MacLeod (’84). Berteanx (’89) and others. 
