444 dr. v. b. white on the [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 p'roduced 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 canuot 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 ; as, anten- 

 nulary sternum ; r, one of the projecting ridges which bound it 

 anteriorly; ff, the groove on its lateral surface ; s, the smooth surface 

 between the groove and the ridge, against which the pad on the 

 antenna rubs ; a r', articular cavity for the right antennule ; a r, arti- 

 cular cavity for the right antenna ; b, basicerite, and /', isehiocerite of 

 the left antenna ; /, the flap. 



Fig. 2. The same, seen from aliove (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: it, inferior or attached edge of pad; xy, 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 Up 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-inch 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 "00 from even the snudl and barren island 



