jrora the Loioer Amazons &c. 81 



be closely allied to Reidyi and Ajidreiosi, but evidentlj quite 

 distinct, if we may judge from Keyserling's figure of the 

 vulva. Of. notes on C. rufibarbis (Perty), Keys., above. 



^feasurements in mi'llim. — Tot. len. 33 2, carap. 13'2 ; legs 

 i. 46-6, ii. 41-9, iii. 33-5, iv. 46 ; pat. + tib. i. 18-5, iv. 16, 

 iii. 12-5. 



Ctenus Keyserlingii^ nom. nov. (^C.ferus (Perty), Keys.). 



The type of this form differs decidedly from both nigri- 

 venter, Keys., and boliviensi's, sp. n., in the form of the vulva 

 (see PI. Hi. fig. ii.c), though the general character is the 

 same. Cf. notes on G. ferus (Perty), Keys., above. 



Measurements in millini. — Tot. len. 30, carap. 17*2 ; legs 

 i. 50-9, ii. 48-3, iii. 37-1, iv.ol-8; pat. + tib. i. 20-5, iv. 18-2, 

 iii. 14-3. 



Ctenus nigriventer, Keys. 



Distinguished from Keyserlingii and boliviensi's by the black 

 ventral surface of the abdomen and a difference in the form 

 of the vulva (PI. III. fig. ii. d). To finally confirm or refute 

 the apparent distinctions between these three forms one needs 

 many more specimens. It is impossible to make definite 

 assertions based on a single specimen of each form. 



Measurements in millini. — Tot. len. 30, carap. 15 ; legs i. 

 44-9, ii. 42-2, iii. 34-3, iv. 468; pat. + tib. i. 17-9, iv. 16-4, 

 iii. 12-8. 



Ctenus medius, Keys., 2 . 



The figure of the vulva given by Keyserling is quite suffi- 

 cient to establish the distinction between this form and the 

 others here recorded, even if the type had not been to hand by 

 way of confirmation. 



A female and a male (the latter described for the first time 

 below, p. 87) were found in a collection from Theresiopolis, 

 S. Brazil. The female is identical with the type of Keyser- 

 ling' s medius. 



Measurements in millim. — ? . Tot. len. 22, carap. 12 ; legs 

 i. 37-5, iv. 42; pat. + tib. i. 13, iv. 12, iii. 10. 



Ctenus nigritus, sp. n., ^ . 



Hob. Forest, Santarem. 



Type in coll. Brit. Mus. Nat. Hist. London, 1896. 

 (J. Total length (including mandibles) 15 mm. 

 Ann. ds Mag. N. Hist. Ser. 6. Vol. xix. 6 



