MVGALOMOBPEUE. 157 



The Opisthothelae :ire divisible into two Suborders, which may 

 be diagnosed as follows : — 



a. Basal segment of mandible projecting 



forwards from the fore extremity of the 

 cephalothorax, its articulation lying in 

 a vertical plane ; tang closing back- 

 wards MyGALOMOBPHjE. 



b. Basal segment of mandible projecting 



downwards beneath the extremity of 

 the cephalothorax, its articulation lying 

 in a horizontal plane ; fang closing 

 more inwards AnAcnNOMORPn^;. 



Suborder MYGALOMORPHjE. 



Basal segment of mandible large, projecting forwards, articulated 

 to the cephalothorax in a vertical plane ; fang closing obliquely 

 backwards. Respiratory organs represented by four operculate 

 pulmonary sacs. Spinning-mamillcB normally four in number — a 

 posterior longer, three-jointed, and an anterior shorter one-jointed 

 on each side ; rarely the latter is absent, and occasionally an 

 additional small anterior mamilla is present, making a total of 6. 

 Sternum marked with 4, rarely 3, pairs of sigilla. Palpal organ in 

 male non-retractile, simple, usually without accessory process. 

 Genital aperture of female without horny plate (vulva). 



Distribution. Temperate and tropical countries. 



Habits. Mostly ground -spiders, living in burrows, and fre- 

 quently closing the aperture with a movable lid. 



The Indian Mygalomorphae are referable to the following 

 families : — 



a. Coxa of palp with large maxillary process; spin- 



ning-mam ilia) (i Atypidae. 



b. Coxa of palp without large maxillary process; 



spinning- maruillae not more than 4. 

 a 1 . Tarsi without ungual tufts; armed with 3 

 claws, the superior of which are strongly 

 toothed. 

 «-. Posterior mamilla) short or moderately 

 long; anterior mamillae close together at 

 base; a rastellum present on mandible. . . . Ctenizidse. 

 J-. Posterior mamilla' very long ; anterior 

 mamillae widely separated at base ; no 



rastellum . . . . " Dipluridae. 



ft 1 . Tarsi with ungual tufts, inferior claw almost 

 always absent ; superior claws at most 

 weakly toothed. 

 d A . Distal segment of posterior mamillse very 



short, rastellum almost always present . . Barychelidae. 

 P. Distal segment of posterior mamillae 1 



and slender, rastellum never present .... Theraphosidae. 



