PBOPAGATION OF CERTAIN ECHINODEEMS. 71 



ment that it is difficult to follow tliera. The Adscera are produced 

 at the expense ot the abundant yelk; and the animals at once 

 take a great start in size by the imbibition of water into the pre- 

 visceral cavity. The young Urchins jostle one another on the 

 floor of the breeding-pouch, those below pushing the others up until 

 the upper set are forced out between the rows of fringing spines 

 of the pouch ; but even before leaving the marsupium, on carefully 

 opening the shell of the young, the intestine may be seen already 

 full of dark sand, following much the same course which it follows 

 in the adult. The size of the test of the young on leaving the 

 marsupium is about 2"5 millims. in length by 2 millims. in width. 



IV. ASTERIDEA. 



On the 27th of January, 1874, at station 149, off Cape Maclear, 

 on the south-east coast of Kerguelen Land, we dredged a hand- 

 some Starfish of the genus ArcJiaster from a muddy bottom 

 at a depth of 30 fathoms. As this species, which is not far re- 

 moved from A. andromeda of the northern seas, appears to be un- 

 described, I will give it provisionally the name of A. excavatus 

 (fig. 10). 



A well-grown example is from 100 to 120 millims. in diameter 

 from tip to tip of the arms ; the length of the arm is about three 

 times its width near the base, and three times the diameter of the 

 disk. The pairs of margiunl plates are long and narrow, running 

 up with a slight curve outwards from the edge of the ambulacral 

 groove until they meet the border of the dorsal perisome above ; 

 they are closely set with short blunt spines, which become gradu- 

 ally a little longer towards the radial groove ; and at the edge of 

 the groove each plate bears a tuft of about six rather long spines : 

 these tufts in combination form a scalloped fringe spreading in- 

 wards on each side over the groove. The dorsal surface of the 

 body is covered with a tessellated pavement composed of capitate 

 paxilli. The heads of the paxilli in close apposition combine to 

 form a mosaic with rudely hexagonal facets ; and as they are 

 raised upon somewhat slender shafts whose bases, like the plinths 

 of columns, rest upon the soft perisome, arcade-like spaces ai-e left 

 between the skin and the upper calcareous pavement. The eggs 

 pass into these spaces from the ovarial openings : on bending 

 the perisome and separating the facets, they may be seen in num- 

 bers among the shafts of the paxilli. There is a continual dis- 



