526 
W. F. PURCELL. 
Turning now to the Araneae verse or Arachnomorph se, 
we find that in nearly every case the second pair of respira- 
tory organs (and in one family the first pair as well) have 
been replaced by tracheae, the exceptions being the small 
family Hypochilidae with two pairs of lung-books and the 
Pliolcidae, in which there are no other respiratory organs 
besides the single pair of lung-books of the genital segment. 
Moreover, there is a deep infolding along the hind edge of 
each of the respiratory segments between the spiracles, so as 
to hide from view the genital opening and the external 
openings of the well-developed ectodermal tendons or enta- 
pophyses of the ventral longitudinal muscles. There are a 
suitor, with the epigastric fold drawn apart so as to expose the 
genital opening and the edges of the septa of the lung-books. These 
two figures are remarkaljle for showing that in these two Arachnids 
the pulmonary saccules of the genital segment open directly into the 
cleft of the epigastric fold, being, in fact, attached to the anterior 
wall of the fold. I examined a female of Thelyphonus caudatus, 
and found the conditions exactly as depicted by Pocock. The pul- 
monary ante-chamber opens along its entire medial side into the 
median part of the epigastric fold, and cannot, therefore, be said to 
form a separate chamber, except in its dorso-lateral prolongation or 
jjortion containing the youngest saccules. In the male (i.e. specimens 
with a sjjine on the second abdominal sternite, teste Kraepelin) of this 
sjjecies, however, I found the conditions different. Here there is a 
longitudinal fold of integaiment on each side between the deep median 
part of the epigastric fold and the anterior pulmonary chambei's, so 
that the latter may be said to form separate chambers op)ening by the 
ventral slit only into the epigastric fold, as is usual in dipneumonous 
spiders. The condition depicted by Pocock in Liphistius is not 
known to occui- in any dipneumonous spider, and may indicate that the 
epigastric fold of this form is directly connected with that of Thely- 
phonus and not of independent origin, in which case the absence of 
the fold in the My galomorphaj would be a secondary condition. Its 
presence in the four-lunged arachnomorphous family Hypochilidae 
is also an interesting circumstance. 
These two figures of Pocock’s should have been included in the his- 
torical list of papers concerning the lung-books of Arachnids given at 
the end of my previous paper (:09). They iinfortunately did not come 
to my notice until after the paper had been sent to the press. 
