PLATE B. 



Fig. 1.— Sternum of Cicada or)ii{?), with portions 

 removed, so as to uncover parts of the sounding organs. 

 m. Muscle, which works the tympanum (c). x. Ab- 

 dominal cavity, filled with air. y. Viscera and dorsal 

 muscles (/,/). After Prof. Lipori. 



Fig. 2. — a. Metathorax, with part of the coxae. 

 //. Eight opercular plate detached, and exposing to 

 view the inner parts, h. Left opercular plate, c. Inner 

 shining annular membrane, or tympanum, d. External 

 portion of the sounding cavity, e. Septum, which 

 divides the internal segment. /. Pellucid or mirror- 

 like membrane, g. Outer fascia of the sternum, which 

 forms the internal wall of the cavity, h. Sternite. 

 After Prof. Lipori. 



Fig. 3. — Corrugated membrane of the tympanum 

 stretched by its muscle, m. The muscle itself, tf. The 

 funicular portion of the tendon. 



Fig. 4. — Diagrammatic section of the thorax of a 

 Cicada, seen from the anterior end. d, d. Corrugated 

 membranes, to the centres of which are attached fine 

 ligaments, through which the parchment-like mem- 

 branes are made to vibrate, m, m. The two fasciculi of 

 muscle, which vibrate the same. v. Vertical mem- 

 branous septum, p. Dorsal cover-plate of the right 

 side ; that of the left has been removed, s, s. Sterna 

 of the first and second somites, with posterior mem- 

 branes stretched between them. After Mr. C. L. Morgan. 



Fig. 5. — Part of the apparatus of the female of 

 Athijsaniis communis, with its double saws (s, s). These 

 consist of two long, thin, chitinous blades, set with 

 teeth on one side, r, r. Portions of the rasp-like 

 laminae. 



