734 MB. F. o. piokaud cambeiugb on [June 16, 



tibia iv. without any cusps or spines. Protarsus and tarsus iv. 

 with a few spines beneath. Pedijialp. Femur and patella without 

 cusps ; protarsus and tarsus armed with numerous marginal cusps 

 on either side. Tarsal c]av\ s three, on pedipalp one only, superiors 

 armed with a small single denticle towards the base beneath. No 

 scopula at all present. 



Spinners four ; posterior pair very short, less than one qunrter 

 as long as abdomen. Second joint half the length of basal ; ter- 

 minal half the length of the second. Anterior pair half the length 

 of basal joint of posterior, one diameter apart, not closely con- 

 tiguous. 



Comparative measurements in millimetres. — 5 . Carapace 7 long., 

 6 lat. Abd. 9 long., 6 lat. Ceph. area 4 long. Coxa of pedipalp 

 2-5 long., 1-5 lat. Stern. 4 long., 3-5 lat. Pedes, long. i. 17 — 

 ii. 15— iii. 16— iv. 21. Artl. i. long. 2'5— 1— 5— 2— 3— 3. Artl. 

 iv. long. 2-5 — 1 — 5-5 — 2 — 4—3-5 — 2. Posterior mam. 2 long.; 

 artl. 1 — -5 — -25. Ant. mam. -5 long., -25 apart. Mandib. 3 

 long. 



A single specimen of _ the female sex was taisen by myself 

 amongst fallen mango-leaves in a clearing in the forest of Santarem 

 in March 1896. 



Species already described from the Neotropical Region. 



Of the various species of Idiopis which have been already de- 

 scribed from South America, some of them possibly belonging to 

 the genus Acanthodon, the following appear to me to be quite 

 different from A. santaremia. 



Idiops rohdei, Karsch ( $ ), Berl. ent. Zeit. xxx. p. 93. $ .long. 

 16 mm. Hah. Paraguay ? — Although most of the characters given 

 in this diagnosis are common to the whole genus, the statement 

 " labio ad apicem irregulariter deiiticulato " certainly does apply 

 to my species. 



IdioiJS fuscus, Perty ( d ), Delect. Anim. Art. 1833, p. 197, 

 tab. 39. (S . Bab. Piauhi, Brazil. — The position of the eyes — 

 " oculi 8 : 2 antici, 2 majores medii, et pone hos 4 in lineam 

 curvam dispositi" — is not the same as in A. santaremia. 



Idiops argus, Sim. ( § ), Ann. Soc. Ent. Pr. 1889, p. 180. 

 $, long. 16 mm. Hub. Venezuela. — The description of the labium, 

 " Pars labialis ad apicem spiculis 5-6 minuta," cleai'ly excludes my 

 species. 



Idiops fulvipes, Sim. ( $ ), Ann. Soc. Ent. Pr. 1889, p. 181. 

 $ , long. 8 mm. Ilab. Venezuela. — Of this species Simon says 

 " PrBBcedenti valde affinis," referring to /. argus, Sim. ; and since 

 he does not refer to the armature of the labium, one must infer 

 that it is similar to that of the closely allied form. 



Idiops bonapartei, Van Hasselt, Tijdschr. Ent. xxxi. 1888, 

 p. 166. 5, long. 14 mm. Ilab. Surinam. — "Labium serie 

 transversa 7-denticulorum armatiim." A. santaremia has but 2. 



Idiops germani, Sim. (cf ), Hist. Nat. Ar. 2nd ed. i. 1, p. 92 



