676 LaurA FLORENCE 
posterior widest part measuring 0.08 millimeter across. It has the shape 
of a capital A in. which the crossbar is a slight curve, convex toward 
the apex of the letter, and on the dorsal surface the space between this 
curve and the apex of the letter 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 ventral 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 by 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 do 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 (1916 b:209) the ‘‘ buccal tube,” by Sikora (1916: 
26) the ‘‘ Haustellumhalbrohre,” and by Peacock (1918:101) the ‘‘ pump- 
ing-pharyngeal tube.”’ The true nature of the connection 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 beat around on itself 
over the esophagus and never fused with the pharynx (pumping pharynx). 
