4,02 Mr. A. S. Hirst 07i a new Ti/pe of 



the Aviculariiiiffi (Phoneyusefe &c.) tlie stridulatory organ 

 (when present) is placed between the posterior surface of the 

 maxiilijialp and the anterior surface of the coxa or trochanter 

 of the first leg. In a few genera in which this latter type of 

 apparatus occurs the part which is borne by the first leg is 

 present on both coxa and trochanter. 



In some of the genera of the Ischnocoleaj there is present a 

 type of stridulating-organ which has hitherto escaped notice 

 and which ditfers in several important respects from those 

 referred to above. In this form of apparatus the structures are 

 situated between the inner (anterior) surfaces of the mandibles 

 themselves. It differs, moreover, from all the forms of 

 stridulating-organs hitherto described as occurring in Mygalo- 

 niorpli spiders in tliat the opposed surfaces of the appendages 

 do not bear dissimilar series of bacillai and spines, the struc- 

 tures of the two halves of the organ being precisely similar 

 in form and arrangement. In the spiders of the genus 

 ISelenogyrus a well-marked apparatus of this type is present. 

 It consists of a number of rows of bacillai arranged in a some- 

 what crescentic manner, the bacillai of the outer rows being 

 the largest. Three or four of the ])osterior bacillas are of 

 large size and form a separate group (fig. 1). In a new 

 genus of Ischnocoleai from the Oameroons, here described, 

 a different modification of this form of stridulating-organ 

 is present. The inner surface of the mandible is furnished 

 with numerous spines which are grouped in a somewhat 

 irregular fashion. A few of these spines are enlarged and 

 are of peculiar form (fig. 2). In an Indian Ischnocolid 

 from Travancore, wliich belongs to an undescribed genus 

 and species, the stridulating-apparatus presents itself in a 

 much reduced form. An oblique row of five strong spines is 

 present towards the base of the inner surface of the mandible. 

 A few weak spines are placed behind this row of strong 

 spines, and some of the setas of the itnier surface of the 

 mandible have their ends slightly enlarged (fig. 3). In 

 Aletriopelma aiirom'tens, Keyserling *, there occurs a peculiar 

 structure which differs much from the stridulating-organs 

 described above. The inner surface of each mandible is 

 provided with a raised area which partly encircles and 

 encloses a dense brush of long and slender bristles. Tiiese 

 bristles are curved, their free ends being directed towards the 

 ventral edge of the mandible. It remains to be seen if this 

 structure is a stridulating-organ. I have only been able to 



* E. Keyserling, ' Die Spiuiieu Amerikas : Bra.siliuuisclie Spiuueii,' 



isoi, p. la 



