M FBESHWATER ENTOMOSTBACA OF N.S.W. 1. CLADOCEKA, 



Key to species of Macrothrix. 



A. Lip-plate lobed triserialis. 



AA. Lip-plate not lobed. 



B. Head finely serrate spinosa. 



BB. Head bearing teeth var. dentata. 



Macrothrix spinosa King. 



First described by King (1852, p. 256). Kedeseribed and figured in detail 

 by Sars (1888, Plate 3, figs. 1-6). 



Female. Carapace, seen laterally, oval in outline; dorsal margin arched, 

 especially posteriorly, ventral curved, ascending to form with the dorsal a slight 

 obtuse prominence. Head large, fairly erect, rostral prominence slight. Cara- 

 pace marked by a faint reticulation, dorsal margin quite smooth, ventral edges 

 serrate, armed with slender spines. Eye large, ocellus small, quadrangular. An- 

 tennules curved, with notches along the anterior edges. Post-abdomen compara- 

 tively small, bilobed, armed with a row of small but strong anal denticles; end- 

 claws very small. Length .6 mm. 



Male. Smaller than the female. Antennules larger and not so curved. 

 First pair of legs as usual armed with a curved hook. 



Playfair (1914, p. 140) notes that in specimens collected at Lismore the 

 dorsal edge of the carapace is minutely serrate, and points out that this is the 

 main character by which Sars distinguishes this species from Macrothrix lati- 

 eornis (Jurine). An important difference between the two species, however, is 

 that M. spinosa has a bilobed post-abdomen, and M. laticornis has not. 



Distribution. — This species has a wide distribution in New South Wales 

 (Centennial Park, Five Dock, Liverpool, Casino, Lismore, Holbrook and Corowa). 

 It also occurs in Queensland, Hawaii, Sumatra, Ja.va, Siam, Singapore, South 

 America and South Africa. 



Var. DENTATA Playfair, 1914 (p. 141, Plate 8, fig. 2). 



Head without hairs but minutely serrate; furnished on the front and dor- 

 sally with teeth not spines. 



Locality. — Lismore. 



Macrothrix triserialis Brady. 



Brady first described this species (1886, p. 295) from specimens collected in 

 Ceylon. A more detailed description Avas published by Daday in 1898 (p. 51, 

 fig. 24). 



Female. Carapace, seen laterally, somewhat oval in shape, broader an- 

 teriorly than posteriorly; dorsal margin slightly arched, ventral more strongly 

 arched and protuberant in the middle, forming a sharp angle and a produced 

 point posteriorly. Head moderately arched, produced below into a small tri- 

 angular rostrum. Eye large, with conspicuous crystalline lenses; ocellus very 

 small, square, situated near the end of the rostrum. Antennules slightly curved, 

 their anterior margins sen-ate. Lip-plate large, bearing four sets of small 

 bristles, the ventral edge produced and bilobed. Surface of the carapace marked 

 by an irregular reticulation and also by tiny pits ; dorsal margin serrate, ventral 

 bearing a series of small teeth arranged in groups of three, between which are 

 slender bristles. Post-abdomen moderately broad, bilobed, the first lobe bearing 

 eight denticles, the second with about twenty denticles, which increase in size 

 posteriorly; end-claws short, curved; fine lateral spinules also present. Length 

 1 mm. Colour pale yellow. 



