ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 175 



Dimorphism in Australian Agrionidae.* — R. J. Tillyard records 

 •dimorphism of the females in two Australian genera. These two con- 

 tain the smallest and weakest species of the dragon-flies known in 

 Australia, a point which the author regards as strengthening the 

 contention that the existence of dimorphic females is in some manner or 

 other connected with the preservation of the species. The forms 

 exhibiting dimorphism are Ischnura delicata Selys 9 and Ar/riocnemis 

 splendida Martin ? . The two genera referred to, though differing 

 widely in their wing-structure, have many points of similarity. 



New Order of Apterygota.f — F. Silvestri describes Acermtomon 

 g.n., represented by A. doderoi sp. n. It was found in humus at Genoa 

 and other localities in Italy. Antennae and cerci are absent ; the oral 

 apparatus is suctorial ; there are eleveu abdominal segments and a very 

 primitive anal segment ; the genital aperture is unpaired on the eleventh 

 urosternite ; there is a supra-anal and a sub-anal lamina ; there are no 

 eyes, but there are two ocelli (?). It is the most primitive insect as yet 

 discovered, and requires a special order — Protura. 



5. Arachnida. 



Maturation and Fertilisation in Theridium.J — T. H. Montgomery, 

 jun., has studied the eggs of a common spider, Theridium tepidariorum, 

 and describes the ovarian ova, the stage of the first maturation spindle, 

 the stage of the second polar spindle, the pronuclei and cleavage nuclei, 

 and the frequent occurrence of polyspermy. 



Studies on Mites.§ — Nathan Banks has made a catalogue, with 

 bibliographical references, of the mites of the United States, which will 

 be of great service to those working at this group. A preliminary list 

 by Osborn and Underwood, published in 1886, included 99 species in 28 

 genera. The present list gives 450 species in 133 genera, " yet this is 

 probably less than a third of the entire Acarid fauna of the United 

 States." It may be noted that a synopsis of genera || was published in 

 1904. 



Hydrachnids. — C. Maglio ^f gives a list, revised and criticised, of 

 Italian Hydrachnids. He has made a number of new records, and the 

 total number of species amounts to 86. 



W. Williamson** records 18 species (in 12 genera) from Scottish 

 Lakes ; Lebertia porosa Sig Thor, and Oxus ovalis Muller are additions 

 to the two previous lists for Scotland, and Huitfeldtia rectipes Sig Thor 

 is a new British record, the genus having been hitherto recorded from 

 Norway only. 



New Species of Eurypterus.ft — Henry Woodward describes, from the 

 Coal-measures to the north-west of Ilkeston, Ewrypterus moyseyi sp. n. 

 and E. derbiensis sp. n. 



* Proc. Linn. Soc. N.S. Wales, 1907, pt. 2, pp. 382-90. 



t Boll. Labor. Zool. Scuola Agric. Portici, i. (1907) pp. 296-311 (18 figs.). 



J Zool. Jahrb., xxv. (1907) pp. 237-50 (2 pis.). 



§ Proc. U.S. Nat. Mus , xxxii. (1907) pp. 595-625. 



|| Op. cit., xxviii. (1904) pp. 1-114. 



i Rend. R. 1st. Lombardo, xl. (1907) pp. 953-74. 

 ** Proc. R. Soc. Edinburgh, xxvii. (1907) pp. 302-7 (7 figs.). 

 -tt Geol. Mag., iv. (1907) pp. 277-82 (1 pi.). 



