22 THE AUSTRALIAN MUSEUM. 



length and 1*5 cm. in diameter. Besides the very powerful sphincters 

 (fig. 3), the rest of the mantle has strong muscle hands running in all 

 directions, and forming a close but irregular network. The muscles are 

 imbedded in gelatinous connective tissue, which is so densely packed 

 with spicules as to have a felt-like appearance. The chief layer of 

 connective tissue and spicules is on the inner side of the mantle. The 

 spicules are shown in fig 5, and are seen to be of at least three sizes, 

 the largest in longitudinal bands, the medium sized in rows running 

 transversely, and the smallest scattered. 



The branchial sac has generally 12 folds on each side, but in one 

 specimen, from Port Stephen, I count 11, and in one from Port Jackson 

 there are 15 on each side, while in another there are 12 on one side and 

 13 on the other. I do not find any with 14, the number given by von 

 Drasche for M. Julinii. 



On PI. Cyn. IV., fig. 2 shows the general appearance of the folds 

 round the oesophageal aperture, fig. 3 shows the lines of spicules on 

 the outer side of the branchial sac, and fig. 4 shows part of the sac 

 from the inside. This is a fairly regular part. In some specimens many 

 irregularities occur. 



The endostyle is very wide and shallow. Spicules are everywhere, 

 short ones in the test, longer in the mantle, several sizes in the branchial 

 sac, largest, perhaps, in the folds, long ones also in the tentacles. 



The tentacular circle is about 2 cm. in diameter. The tentacles are 

 in all cases very large (up to 2 cm. in length) and much branched 

 (PL Cyn. IV., fig. 2), but they vary a little in number in the different 

 specimens. Twelve larger and twelve smaller is certainly the usual and 

 characteristic arrangement, but I have seen 10 of each, and in one case 

 can only find 17, several of the smaller ones being evidently absent. 



The dorsal tubercle may be from 7 mm. to 1 cm. in diameter, and is 

 to the eye a convex circular elevation with a minutely marked spongy 

 surface. Slight magnification with a lens shows that the usual slit is 

 curved in meandering lines all over the surface, so as to form a close 

 pattern (fig. 5). The large alimentary and reproductive viscera are 

 completely imbedded in the thick mantle so as to be scarcely visible. 

 There are specially large spicules in the mantle around the stomach 

 and the ovaries. 



I have left to the last the curious character that the dorsal lamina in 

 place of being a plain smooth-edged membrane, is represented by a 

 series of very small languets. Strictly speaking, this character ought to 

 remove the present species from the genus Microcosmus and put it in 



