48 THE AUSTRALIAN MUSEUM. 



from. We have about two dozen, of various shapes, and with various 

 lengths of stalk. Three, of which one is sessile, adhering to a Poly- 

 carpa rigida, are shown in fig. 1, another with a longer stalk and more 

 covered with sand, is given in fig. 5, while fig. 7 shows a specimen 

 entirely encrusted with sand. Very few of the specimens are so green as 

 the " Challenger " ones, and a few of the sandy ones (figs. 5 and 7) have 

 the test more of a dirty yellow than a green colour. 



The dorsal tubercle, while always simple, varies a little in outline, and 

 direction of opening. One is figured (fig. 6) which is not quite like that 

 of the "Challenger" Report, while others have one horn turned out- 

 wards. In all other particulars our present specimens agree with the 

 original description." It may be added, however, that the smaller 

 tentacles are generally 3 between each pair of larger ones, and of the 

 3, the central one is longest (fig. 9). The irregular membranous 

 expansion of the transverse vessels alluded to in the "Challenger" 

 Report, takes the form in some of these specimens of a number of simple 

 and compound bud-like processes, growing out from both the transverse 

 and the fine inter-stigmatic vessels (fig. 8). Another interesting detail 

 of structure about the branchial sac is the curiously vesiculated structure 

 of the outer edge of the internal longitudinal bars, shown in fig. 8, under 

 a high magnification. Finally, at the base of the atrial siphon, is a 

 membranous diaphragm, which bears a series of minute atrial tentacles 

 (fig. 10). 



It may be said that there are 2 series, or varieties, amongst these 

 specimens the sandy ones with yellowish tests, and brown mantles, and 

 branchial sac, and those that have very little sand, and show more or 

 less green in both test and mantle ; but there are no constant points of 

 structural difference that would enable these to be defined as distinct 

 species. 



Polycarpa sacciformis, n. sp., PL Cyn. XIX., figs. 14. 



External appearance. Body oblong and erect, compressed laterally. 

 Anterior end narrowest, almost pointed ; posterior end broad and rounded; 

 dorsal edge rather convex, ventral somewhat concave. Slightly attached 

 by posterior end, towards dorsal edge. Branchial aperture at end 

 of short siphon, terminal at ventral edge, directed anteriorly; lobes 

 indistinctly marked. Atrial aperture at end of short siphon, on dorsal 

 edge, about one-third of way from anterior to posterior end, projecting, 

 directed dorsally and anteriorly ; 4-lobed, lobes distinct. Surface rough, 



*" Challenger " Report, p. 168. 



