60 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
natural group within the genus, and differ from the two species just 
described and all others known to the author as follows : flies of small 
size; breadth of front at narrowest part at least two thirds eye width; 
rows of frontal bristles parallel, though last ventral pair sometimes 
diverge slightly toward eye orbits; lamellae of fourth ventral plate 
without 'brushes' and widely separated; penes slender; median 
process extending farther forward than laterals and practically en- 
tirely chitinized; lateral processes entirely chitinized and blackish in 
color. 
3. Ravinia quadrisetosa (Coquillett). 
PI. 4, fig. 27; PI. 7, fig. 46. 
1900. Helicobia quadrisetosa Howard, Proc. Wash. Acad. Sci., vol. 2, p. 568. 
Note of habits. 
1901. Helicobia quadrisetosa Coquillett, Ent. News, vol. 12, p. 17. Descrip- 
tion. 
1904. Helicobia quadrisetosa Baker, Invert. Pacifica, vol. 1, p. 3. Occurrence. 
1911. Sarcophaga (Helicobia) quadrisetosa Greene, Ent. News, vol. 22, p. 384. 
Occurrence. 
1912. Sarcophaga (Helicobia) quadrisetosa Pratt, Can. Ent., vol. 44, p. 181. 
Occurrence and habits. 
1912. Helicobia quadrisetosa Hunter, Pratt, and Mitchell, Bull. U. S. Bur. 
Ent., no. 113, p. 49. Occurrence and habits. 
1913. Helicobia quadrisetosa Johnson, Bull. Amer. Mus. Nat. Hist., vol. 32, 
p. 75. Occmrence. 
Type: U. S. National Museum, no. 5395. 
Breadth of front at narrowest part about two thirds eye width; 
lateral vertical bristles absent; anterior face of posterior femur 
typically with two rows of bristles, if intermediate row is present, it is 
vestigial; submesotibial bristle absent; first and third veins bristly; 
four pairs postsutural dorsocentrals but last two pairs the longest. 
Lamellae of fourth ventral plate widely separated, without 'brushes.' 
Length: 4 to 6 mm., average about 6 mm. 
Head. — Viewed from side parafrontals and genae with dark re- 
flections. Breadth of front at narrowest part about two thirds eye 
width; cheek height approximately one fourth that of eyes. Front 
prominent ; inner orbits of eyes on its upper part parallel or converging 
very slightly downward ; sides of frontal vitta parallel, a little drawn in 
at base, second antennal joint brownish at tip; third about twice 
length of second; arista plumose on basal two fifths or one half. 
Back of head somewhat convex; three rows of black cilia behind eyes; 
