158 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
delicate crest projects downward from this traverse. The male 
Culex has the same arrangement of thickened areas but lacks the 
crest. The development of these thickened areas in the walls of 
the pharynx near its union with the antlia must make the ventro¬ 
lateral plate rigid at this point. The antlia has also at its anterior 
end rather unyielding walls. Hence the thin dorsal plate beyond 
the posterior hard palate forms an efficient pharyngeo-esophageal 
valve, dipping into the lumen of the canal through elasticity and 
dyeing withdrawn by muscles. 
At its anterior end the pharynx for a space is firmly bound to the 
walls of the head by an ascending chitinous plate on either side. 
These plates are continuous with the cuticle of the head and the 
intima lining the pharynx, and represent intracephalic continuations 
of the plates formed by the union of the genae with the clypeus 
(pi. 13, fig. 3-5). The plates soon degenerate into low crests along 
the dorso-lateral angles of the pharynx and fade out. 
At its hinder end the pharynx is held in place by two pairs of 
muscles. The shorter of these, the lateral pharyngeal muscles, run 
outward from the external face of the spurs at the rear of the phar¬ 
ynx to the tentoria. The others, the ascending pharyngeal muscles, 
pass from the internal face of the spurs to the vertex of the head. 
The pharynx as a pumping mechanism is constructed on the same 
principle as the salivary pump or antlia. The lumen is diminished 
by the inspringing of the chitinous dorsal plate, which is withdrawn 
again by the action of muscles. The muscles which lift the roof of 
the pharynx in this pumping action may be called the elevators of 
the palate (Nuttall and Shipley, :01-: 03). When compared with the 
homologous muscles of many flies these muscles appear relatively 
weak. They are considerably specialized, however, as there are five 
distinct pairs, instead of a single mass or at most a larger anterior 
and a smaller posterior section. When this latter differentiation 
occurs the posterior section is called the protractor of the pharynx 
(Meinert, ’81). Possibly it finds its equivalent in the fifth pair of 
the Culicid muscles. Of the five pairs, the anteriormost insert on 
the rear of the anterior hard palate region, the next on the soft pal¬ 
ate, the three posterior pairs on the hard palate. The pharyngeo- 
esophageal valve is elevated by a pair of valvular muscles from the 
frons. These lie caudad from the buccal ganglion. The valvular, 
ascending pharyngeal, and lateral pharyngeal muscles are described 
