676 Laura Florence 



posterior widest part raeasurinp; 0.08 millimotcr across. It has the shape 

 of a capital A in which the crossbar is a slifi;lit curve, convex toward 

 the apex of the letter, and on the dorsal surface the space between this 

 curve and the apex of the l(>tter is solid. Its total length from the anterior 

 edge to the posterior end of the arms is approximately 0.22 millimeter. 

 Laterally it curves downward and centrad, but the opposite sides do not 

 meet, so that on the venti-a-l surface there is an open slit continuous with 

 the buccal slit. The posterior arms of the buccal plate are fused with 

 the lateral wall of the pumping pharynx. 



The pumping pharynx 



The pumping pharynx (Plate LX, 2 and 3) is strongly chitinized on the 

 ventral and lateral surfaces and is capable of considerable dilatation 

 on the dorsal surface. Its width at rest is 0.06 millimeter and the com- 

 bined length of the buccal plate and the pumping pharynx is 0.5 millimeter. 

 Its ventral surface extends forward to the posterior end of the ventral 

 slit of the tubelike part of the buccal plate, and its dorsal surface is con- 

 tinuous with that of the buccal plate. Toward the posterior end there 

 is a somewhat knoblike projection of the lateral walls, followed b.y a rather 

 short backward prolongation of the more strongly chitinized part at the 

 junction of the pumping pharynx with the true pharynx. 



The pumping pharyngeal tube 



From the anterior end of the pumping pharynx, two half tubes (Plate 

 LX, 1 and 2) pass into the groove of the buccal plate but tlo not extend 

 quite to its anterior end. Their ventral edges overlie each other; their 

 dorsal ends lie apart, but so close under the buccal plate that a tube is 

 formed through which blood is drawn during feeding. This tube has 

 been called by Harrison (191Gb: 209) the "buccal tube," by Sikora (19115: 

 26) the " Haustellumhalbrohre," and by Peacock (1918:101) the " pump- 

 ing-pharyngeal tube." The true nature of the coimection between this 

 tube and the pumping pharynx can be followed only in sections, and is 

 discussed later. 



The pharynx 



The pharynx (Plate LX, 1 and 2) was called by Enderlein (1904:127) 

 the " larynx," and he described it as a chitinous band bent around on itself 

 over the esophagus and never fused with the pharynx (pumping pharynx). 



