50 THE AUSTBALIAN MUSEUM. 



essential respects with the description in the "Challenger" Keport.* 

 The specimen measures 4 by 3 by 3 cm. (PI. Cyn. XIX., fig. 5). The 

 dorsal tubercle, although described, was not figured in the "Challenger" 

 Report, so I give a figure of it now (fig. 6). 



Polycarpa Jacksoniana, n. sp., PI. Cyn. XIX., figs. 79. 



External appearance. Form ovate, nearly globular, attached by left 

 side. Branchial aperture at end of long siphon on anterior dorsal edge, 

 directed forwards and dorsally. Atrial aperture on dorsal edge, half way 

 down, directed backwards, on short thick siphon. Openings indistinct, 

 4-lobed. Surface nearly covered with sand, pieces of shells and sea- 

 weed, and somewhat wrinkled. Colour brown. Length 4-5 cm., 

 width 3-5 cm., thickness 2 cm. 



Test leathery, thin but stiff, dark brown on outer surface, whitish and 

 glistening on inner surface. 



Mantle adheres slightly to test ; thick ; musculature rather strong. 



Branchial sac, 4 folds on each side. About 7 longitudinal bars on 

 each fold, and about 6 in the interspaces. Every 7th transverse 

 vessel wider than intermediate ones; 5 to 7 stigmata in each mesh. 

 Meshes elongated transversely. 



Dorsal lamina a narrow plain membrane with even edge. 



Tentacles simple, 24 in number, arranged symmetrically ; 6 longer, 

 with 3 smaller between each pair, middle one of the 3 rather longer 

 than its neighbours. 



Dorsal tubercle simple, somewhat horse-shoe shaped, one horn coiled 

 inwards, the other outwards. 



Locality, Port Jackson. 



This species (PI. Cyn. XIX., fig. 7) has a test rather like that of a 

 typical Microcosmus leathery and wrinkled, with adhering sand, 

 shells, &c. Figs. 8 and 9 show the branchial sac and dorsal tubercle. 

 They do not call for any further remarks. 



This species is probably closely related to P. longisipJionica. 



Polycarpa pilella, Herdman. 



This species was described from specimens obtained during the 

 " Challenger " Expedition, off Bahia, in Brazil. On the surface of some 

 of the large specimens of Microcosmus Draschii, from Port Stephen, 

 there are a number of minute sandy balls, which prove to be a species of 

 Polycarpa. I have not found any gonads in those I have examined, so 



* Part I., p. 177,1882. 



