454 



3. Linnean Society of New South Wales. 



Abstract of Proceedings, July 26th, 1905. — 1) On Dimorphism in the 

 female of Ischnura heterosticta Burm. [Neuroptera: Odonata]. By R. J. Tilly- 

 ard, B.A. — In February last, at Cook's River, about a dozen beautifully 

 coloured examples of the pretty little dragonfly, Ischnura heterosticta Burm., 

 which appeared to be males, were captured, together with half a dozen females 

 of the ordinary dull blackish type. On examination it was found that, with 

 the exception of three, all the supposed males were in reality a second form 

 of female (Form B) closely resembling the male. It is intermediate in shape 

 between the male and the typical female (Form A), the abdomen being thicker 

 than in the male, but with the tip distinctly enlarged; while in colouring it 

 almost exactly resembles the male, but bears not the slightest resemblance 

 to the typical female. Both forms, however, possess the pale pterostigma on 

 the forewing, whereas in the male this is black. One of two things seems to 

 have happened: — Either, firstly, Form A is the original specific female, in 

 which case Form B may have been evolved as a protective form, mimicking 

 the male because of the latter's immunity from destruction; or, secondly. 

 Form B, resembling the male so remarkably, was the original specific female, 

 in which case Form A may have developed its sombre colouring as a pro- 

 tective garb for the preservation of the species, the typical female being par- 

 ticularly liable to destruction from its brilliant coulouring. It may be then 

 supposed that the male, being less palatable and attractive, had no need of a 

 protective guise, and therefore remained constant in form and colouring. If 

 the second supposition be correct, it might be expected that the protective 

 form of the female would become more abundant and more fertile than the 

 unprotected form. This is at jjresent the case. Form A being by far the more 

 abundant, and the stouter and more developed abdomen indicating greater 

 fecundity. — 2) Notes on the Older Tertiary Foraminiferal Rocks on the 

 West Coast of Santo, New Hebrides. By Frederick Chapman, A.L.S., 

 F.R.M.S., National Museum, Melbourne. (Communicated by Professor T. 

 W. Edgeworth David.) 



The examination of the oldest sedimentary rocks seen and collected by 

 Mr. Maws on in the Island of Santo proves them to be of Miocene age 

 (Aquitanian and Burdigalian). A point of particular interest brought out by 

 the present investigations is the association of Lepidocyclina with the excen- 

 tric forms oî Miogypsina in the New Hebrides. According to H. Douvillé^ 

 the latter make their appearance after the Lepidoclycina in the Miocene of the 

 South-west of France; although the regular form M. hurcligalensis is contem- 

 poraneous with that genus in beds of Aquitanian age (basal beds of Miocene). 

 The next stage in ascending order, the Burdigalian, is in the same area cha- 

 racterised by Miogypsina globulina, M. irregularis and M. complanata. In the 

 Miocene rocks of Santo , however, both the excentric and the regular forms 

 occur in the same deposit, namely, the foraminiferal tufaceous rock under- 

 lying the massive Lepidocyclina limestone at Wai Malikoliko. From this we 

 naturally infer that faunas, distinct in the European area, were living toge- 

 ther in the New Hebrides Miocene sea. A similar association of species oc- 

 curs here as in the Miocene limestones of Christmas Island , and also of 



1 Bull. Soc. Géol. France Sér. 4. Vol. II. 1902. p. 312. 



