MVGALOMOBPEL*;. 157 



The Opisthothelae are 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 ; fang closing back- 

 wards MYGALOMOEPH.S?. 



b. Basal segment of mandible projecting 



downwards beneath the extremity of 

 the cephalothorax, its articulation lying 

 in a horizontal plane ; fang closing 

 more inwards . . ABACHUOMORPH.*:, 



Suborder MYGALOMORPH^E. 



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-mamillce 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 Mygalomorphse are referable to the following 

 families : 



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



ning-mamillae 6 Atypidae. 



b. Coxa of palp without large maxillary process; 



sphming-mamillae not more than 4. 

 a 1 . Tarsi without ungual tufts ; armed with 3 

 claws, the superior of which are strongly 

 toothed. 



a 2 . Posterior mamillae short or moderately 



long ; anterior mamillae close together at 



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



6 2 . Posterior mamillae very long ; anterior 



mamillae widely separated at base ; no 



rastellum Dipluridae. 



i 1 . Tarsi with ungual tufts, inferior claw almost 

 always absent ; superior claws at most 

 weakly toothed. 

 a 3 . Distal segment of posterior mamillaa very 



short, rastellum almost always present . . Barychelidae. 

 b 3 . Distal segment of posterior mainillae long 



and slender, rastellum never present .... Theraphosidae 



