402 Mr. A. S. Hirst on a new Type of 



the Aviculariinae (Phoneyuseae &c.) the stridulatory organ 

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

 maxillipalp 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 Ischnocolese there is present a 

 type of stridulating-organ which has hitherto escaped notice 

 and which differs 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- 

 morph spiders in that the opposed surfaces of the appendages 

 do not bear dissimilar series of bacillae 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 

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

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

 what crescentic manner, the bacillae of the outer rows being 

 the largest. Three or four of the posterior bacillae are of 

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

 genus of Ischnocoleae from the (Jameroons, 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 arc 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, which 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 setae of the inner surface of the 

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

 Metriopelma auronitens, 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. These 

 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 Spinnen Ainerikas : Brasilianische Spinneii,' 

 1891, p. 16. 



