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Show 444 DR. v. B. W H I T E O N T H E [May 7 distance down, a wavy appearance, corresponding with the ridges into which the surface is raised. The stridulation is almost equally audible in water and air. As to its production by the living animal, Dr. Mobius states that it was heard by himself and Mr. Lloyd In the Hamburg Aquarium, and that it was made especially when the Palinuri were handled; he compares it to the sound produced by pressing the upper leather of a boot against a table-leg. I also heard the sound, and observed the movement of the antenna producing it, in a specimen brought alive to the Biological Laboratory of the School of Mines shortly after making my last communication. As Dr. Mobius observes, the sound cannot be produced in spirit specimens. These can, however, be again rendered vocal by soaking them for a longer or shorter time in water. EXPLANATION OF PLATE XXX. Fig. 1. The parts concerned in the formation of the stridulating organ, seen from the right side (nat. size) : o s, ophthalmic sternum ; a s, antennulary sternum; r, one of the projecting ridges which bound it anteriorly; g, the groove on its lateral surface ; s, the smooth surface between the groove and the ridge, against which the pad on the antenna rubs ; ar\ articular cavity for the right antennule ; at; articular cavity for the right antenna ; b, basicerite, and i, ischiocerite of the left antenna; f, the flap. Fig. 2. The same, seen from above (nat. size). Letters as before. Fig. 3. The basicerite and ischiocerite of the left antenna, seen from the inner side (nat. size); the dotted line shows the extent of the uncalcified portion of the basicerite: p, the ridged pad ; t, the guiding tubercle. Other letters as before. Fig. 4. The pad, with the guiding tubercle and part of the flap (X 4); the arrow shows the direction taken by the hairs on the inner surface of the flap: i i, inferior or attached edge of pad; x y, line showing direction of movement. Other letters as before. Fig. 5. Diagramatic cross section of the stridulating apparatus, showing the condition of the "parts, (A) when the antenna is moving downwards, (B) when it is moving upwards. The arrows show the direction of movement, b upper and b' lower hp of the uncalcified slit in the antenna. Other letters as before. Fig. 6. Microscopical section of the pad, taken across the ridges. Drawn under a J-incn objective. 2. Contributions to a Knowledge of the Hemipterous Fauna of St. Helena, and Speculations on its Origin. By F. BUCHANAN WHITE, M.D., F.L.S. [Received April 8, 1878.] (Plate XXXI. PART I. SPECULATIVE. "The extreme isolation of St. Helena-which is nearly 1200 miles from the nearest point of the African continent, 1800 from that of South America, and about 700 from even the small and barren island |