232 Ona new Sound-producing Organ in a Spider. 
upon the type of Tegenaria antipodiana described by White 
nearly half a century ago. A glance showed me that this 
spider belongs to the genus Cambridgea of L. Koch; but the 
most interesting fact revealed by an examination of the speci- 
men was the presence of a conspicuous, although hitherto 
unnoticed, organ, which appears to be a sound-producer of 
considerable power. Upon depressing the abdomen and 
looking at it from the front a large cave-like hollow over- 
hanging the pedicel may be noticed. The roof of this exca- 
vation is hairless, smooth, and horny, and is sculptured out 
into a series of six black, shining, strong, transverse arches or 
ridges, which become gradually shorter as they recede from 
the mouth of the hollow to its opposite end. The scraper 
that rubs against these ridges is a large heart-shaped tooth 
that rises from the anterior of the two sclerites which 
strengthen the upper surface of the pedicel. The pedicel, 
both above and below, is rather strongly supported by 
chitinous pieces, that on the lower surface being Y-shaped, 
the stem of the letter representing the anterior rod, which is 
immovably fused with the posterior apex of the sternum, 
while the arms correspond to two pieces which embrace the 
sides of the stalk. The upper surface of the stalk is furnished 
with the ordinary posterior median piece, which at the sides 
is contiguous with a pair of thicker sclerites, and the anterior 
piece, as mentioned above, is converted into the upstanding 
heart-shaped tooth, the point of which is thickened and 
slightly recurved. 
That the function of this new organ is to produce sound 
can, | think, hardly be disputed. In its position and in some 
of the details of its structure it resembles that of the stridu- 
lating Theridiide (Steatoda) *. In the latter there is, at the 
base of the abdomen, a circular depression, the edge of which, 
in the males at least, is armed with re-entering teeth. By 
the movements of the abdomen these teeth are scraped against 
a series of ridges and grooves upon the posterior area of the 
carapace, and give rise to a sound. Similarly I conceive that 
in the case of Cambridgea sound must result from the rubbing 
of the arched ridges backwards and forwards across the 
upstanding tooth upon the pedicel. 
But a further resemblance between this new organ and 
that of Steatoda consists in its being confined to the male 
sex f. ; 
* Vide F, M. Campbell, Journ. Linn, Soc., Zool. xv. p. 152 (1880). 
+ For an opportunity to establish this fact I am indebted to the 
Rey. O. P. Cambridge, who kindly sent to me for examination three 
specimens of the genus which he hasin his collection. ‘The first of these, 
