EPHYDRINA. 159 



fFace on each side with, a long bristle; lateral border of the mouth. 



without bristles. PAKYDRA Stenh. 



5 j Face on each side with several long bristles ; lateral border of the 



mouth with bristles. HALMOPOTA Hal. 



Division 2. Clypeus retracted in the oral cavity. 



- ( Claws almost straight, pulvilli indistinct. EPHYDRA Fall. 



\ Claws curved, pulvilli distinct. 2 



2 ( Oral border quite bare. ILYTHEA Hal. 



( Oral border with bristles. 3 



o ( Antennal bristle bare. TICHOMYZA Macq. 



\ Antennal bristle not bare. 4 



4 ( Antennal bristle pubescent. SCATELLA R. Desv. 



\ Antenual bristle pectinated. CJENIA R. Desv. 



The North American Ephydrina known to me belong to the 

 five genera : Oclithera, Brachydeutera, Parydra, Ephydra, and 

 Scatella. 



Gen. I. OCIITIIERA LATR. 



One of the most distinct genera of Ephydrina. Front very 

 broad; antennal bristle above, with three rays. Face above 

 moderately broad, with two furrow-like longitudinal impressions 

 approaching each other very much on the middle, then diverging 

 from each other as they descend, and finally continued in a direc- 

 tion parallel to the lateral border of the mouth ; on the surface of 

 the face there are some fine and short hairs, but no bristles at all. 

 The face and cheeks descend very deep beneath the large promi- 

 nent eyes, but are again contracted sensibly towards the opening 

 of the mouth, rendering it smaller than in any of the other genera 

 of Ephydrina. Clypeus having the form of a small flat lamella, 

 projecting beyond the anterior border of the mouth. The fore 

 coxa3 a little prolonged ; the fore femora exceedingly swollen, 

 furrowed on their under side for the reception of the curved tibias, 

 which terminate in a spine, and beset with a few small bristles ; 

 the first joint of the hind tarsi more or less thickened. The costal 

 vein of the wings reaches to the fourth longitudinal vein ; the 

 second segment of the costa is proportionally very long; the pos- 

 terior transverse vein is very oblique ; the third and fourth longi- 

 tudinal veins converge rather remarkably towards their ends. 



Observation. Th. Say has described a fly as Oclithera empifor- 

 mis ; but on a closer consideration of his observations on the an- 

 terior femora, the color of the insect, and its small size, it becomes 



