June, I9I2.] Towxsend: Muscoid Flies. 115 



For convenience of description the segments will be referred to as the 

 first to thirteenth, which are the apparent segments. First segment 

 (pseudocephalon) small and tubercular, often retracted; segments 

 three to twelve are chitinized on sides and dorsum. Segments five to 

 eleven are composed apparently of six sclerites, or plates each; one 

 dorsal, one ventral, and two lateral on each side. Segment four is 

 probably composed thus, but does not show the plates so clearly. 

 The posterior margins of dorsal plates of segments three to eleven 

 overlap the anterior margins of the succeeding dorsal plates in each 

 case. The ventral plates are whitish and membranous. The dorsal 

 plates are deeply tinged and chitinized, the dorsolateral more deeply 

 chitinized, and the ventrolateral hardly less so. Dorsal plates three to 

 eleven show in hind margin eight small round holes or light unchiti- 

 nized spots, which are probably the scars or origins of detached 

 bristles, three being usually in a triangle on each side and one outside of 

 them. The ventrolateral plates each bear one of these hole-like dots 

 in hind margin. The ventral plates show none, but are covered with 

 very minute, short, dot-like spines with a row of longer spines on front 

 border. The dorsolateral plates each bear one of the hole-like dots. 

 The lateral plates are so arranged as to show one lateral row of 

 double leaf-like plates lying apparently free, the posterior edges of 

 one set overlapping the bases of the next, as may be seen in the 

 below-mentioned figure, extending thus the length of body on each 

 side from segments four to eleven inclusive. Segment thirteen is 

 terminated by four rather sharp tubercles in a horizontal row, each 

 surmounted by a spine-like bristle, the outer one on each side being 

 stronger than the two inner ones. The small lateral plates of segment 

 twelve, which consist of only one on each side, taper posteriorly to a 

 point and are surmounted by a bristle. Between these, but on the 

 dorsum of thirteenth segment, are the two anal stigmatal plates, ap- 

 pearing as two small rounded tubercles, and just in front of each is 

 a very small shortened tubercle surmounted by a very short seta. 

 Each anal stigmatal plate bears four bristle-scars on its periphery, and 

 outside the area of the stigmatal openings. The first two segments 

 and anterior half of third are covered with the same minute dot-like 

 spines as the ventral plates. The cephalopharyngeal skeleton occupies 

 the first to fourth segments inclusive, and shows a strong approach to 

 those of Spathidexia and Ophirion. The upper wing of pharyngeal 



