i9ii] 



NORDAMERIKANISCHE HyDRACHNIDEN. 



289 



Panisus cataphractus Koen. 

 Syn. Thyas cataphracta Koenike; Abh. Nat. Ver. Bremen, 1895, XIII 

 Bd., S. 196-198, Taf. II, Fig. 33-35- 

 Repeated efforts to confirm the presence of a fifth unpaired eye in 

 this Hydracarine were unsuccessful, so that I must now regard the absence 

 of such an organ in this species as an estabUshed fact. It is thus, of course, 

 incorrectly placed in the genus Thyas, belonging much more properly 

 to the genus Panisus. 



Megapus crassipalpis Koen. 

 Syn. Atractides ovalis Koenike : Abh. Nat. Ver. Bremen, 1895, XIII 

 Bd. S. 211, Taf. Ill, Fig. 58 and 59. 

 Megapus crassipalpis Koenike: Abh. Nat. Ver. Bremen, 1908, XIX 

 Bd., S. 246. 



Megapus ovalis (Koen.) 



Length of body 500//. 



Capitulum 99M long, with dis- 

 tinctly projecting rostrum. 



Maxillary palpus 265/* long. 



Fourth segment of palpus dor- 

 soventrally 25/u, thick. 



Spine on the internal part of 

 the flexor side of the 4tn palpal 

 segment 25/i. from the distal end 

 of the segment, rather slender, 

 1 5/i long, straight and not pectinate. 



Epimeral region, 24Q1X long. 



The first pair of epimera fused 

 with one another behind the max- 

 illary emargination, 149^^4 long. 



The outer margin of the last 

 epimera in front of the articular 

 fossa of the last pair of legs dis- 

 tinctly excavated. 



The anterior leg 630/x long; its 

 terminal segment strongly bent 

 and 20/i thick. 



The penultimate segment of the 

 anterior leg 166/* long, 45/x thick 

 at the distal end, which bears on 

 its flexor side two unequally broad 

 ensiform bristles. 



Megapus crassipalpis (Koen.). 



Length of body 500/i. 



Capitulum 116/* long, without 

 projecting rostrum. 



Maxillary palpus 2i5/[z long. 



Fourth segment of palpus dor- 

 soventrally 37/i thick. 



Spine on the internal part of 

 the flexor side of the 4th palpal 

 segment 35/x from the distal end 

 of the segment, of considerable 

 thickness, 25/* long, markedly bent 

 and finely pectinate on both sides 

 in the outer half. 



Epimeral region JiSfi long. 



The first pair of epimera fused 

 with one another behind the max- 

 illary emargination, 249/A long. 



The outer margin of the last 

 epimera slightly convexly bent 

 throughout its length. 



The anterior leg 630^14 long; its 

 terminal segment strongly bent 

 and 2$fM thick. 



The penultimate segment of 

 the anterior leg 182/i long, 50/A 

 thick at the distal end, which bears 

 on its flexor side two unequally 

 broad ensiform bristles. 



