46 



and about two-third>: .IS long as its width. The chitinous band across the back 

 bends round at the > des, and on the belly runs backwards and inwards, reaching 

 down almost to the sexual openintr, whieh has a peculiar guard formed by the 

 sternite or chitinous bow in front of the sexual plate, joining at both ends with 

 the epimera of the fourth pair of extremities. The epimera of the first pair 

 join in a point behind the rostrum. 



The first pair of extremities has the olecranon process on the second joint 

 large, the spine on the fourth aborted, that on the fifth well developed. On the 

 second extremity the olecranon is absent, the spines on the fourth and fifth joints 

 strong. The fir.st joint is something the shape of an equilateral triangle, an angle 

 barely reaching the outer side of the leg. The third extremity is long, with the 

 first four joints of about equal width, the fourth being, perhaps, slightly the 

 widest ; the fifth is small but bears a long curved claw. The finger-like process 

 present in the closely allied species A. digitatus is here absent. The fourth pair 

 of extremities long, stretching when extended considerably beyond the poste- 

 rior end of the abdomen. 



The position of the two long posterior dorsal bristles is peculiar. Instead of 

 arising close beside each other, as in most species, they are inserted one behind the 

 other, about -06 mm. apart, the hinder one being a little nearer the middle line of 

 the body than the other and immediately between the points of insertion of the 

 fourth pair of extremities. The posterior bristles are present three in number on 

 each side, the two inner ones on each side being rather long. 



Female. — Larger than tlie male, being -38 mm. long and -17 broad. It can 

 easily be distinguished by the strong olecranon process on the first extremity and 

 by the eigbt comparatively strong bristles on the dorsal surface. It is found on 

 the King bird — Tyrannus Carolinensie. 



DIMOEPHUS, Haller, 1878. 



"Third pair of feet enlarged, always without claws, but with sucking disks ; 

 the first two pairs but seldom with olecranon process, always with more or less 

 projecting spiny processes. Abdomen with the posterior end always deeply in- 

 dented." 



Dimorphus aculea'uf, Haller. This species was found on the Bluejay — Cya- 

 nurus cristatus. 



Dimorphus Tyrellii, Haller., was found on the Catbird — Mimus Caroli- 

 nensis. 



Dimorphus gladiator, Haller., was found on our common wild pigeon — Ecto- 

 pistes migratorius. 



Dimorphus forcipatus, Haller., was found on the spotted sandpiper — Trin- 

 goides macularius, and on the white-rumped sandpiper — Trinea Bonapartei. 



Dimorphus j>ici majorif, Buchholz, was found on the Big Sapsucker — Picus 

 villosus. 



DIMORPHUS ALBIDUS, n. sp. 

 Fig. 4. Pl. i. 

 ]\liile. — General shape of the body somewhat oval with a length of -.^8 mm.) 

 and a breadth of -19 mm. The abdomen about as long as the breadth of the 

 bod}', and about three times as long as the distance between the second and third 

 extremities. The epimera are long and strongly coloured, those of the first pair 

 of extremities joining very near the front and running back in a long point; 

 between the fourth pair the inconspicuous sexual opening is situated. The cop- 

 ulatory suckers are situated a little more than half way back on the abdomen, 

 which is rather deeply indented, the hindermost part appearing as a clear film. 

 On each side are five bristles, the second and third from the middle being much 

 the largest. 



