528 " THETIS " SCIENTIFIC RESULTS. 



ASTROPECTEN PECTINATUS. 



(Plate xlviii.) 



Astropecten peclinatus, Sladen, Journ. Linn. Soc, Zoo!., 1883, 

 xvii., p. 251. 



1 specimen from Station 21. Newcastle Bight, 28-40 fathoms;, 

 fine grey sand. 



7 specimens from Station 2-5. Oif Newcastle, 42-48 fathoms ; 

 soft mud. 



1 specimen from Station 36. Off Botany Bay, 20-23 fathoms ;. 

 sand to rock. 



1 specimen from Station 41. Off Wata Mooli, 52-71 fathoms ; 

 soft mud. 



1 specimen from Station 52. In Shoalha\en Bight, 19 20 

 fathoms ; sand to mud. 



5 specimens from "off Broken Bay" C? Station 13). 



This series of specimens, ranging in diameter from 55 to 175mm ,. 

 is of particular interest, because it shows that the specimens upon 

 which Sladen based his species were only half grown and that the 

 fully grown individuals (PI. xlviii., figs. 1-2) are so different, they 

 have long passed under another name. In the small specimens, 

 R^3'5r; in specimens with 11=60-80 mm., Il=4-4-5r ; and in 

 large specimens, R equalling about 100 mm., R=5r. Moreover, 

 in young specimens the rays taper to quite a slender point, while- 

 in the adult they are proportionately much wider at the tip. In 

 the adults also the outer spine of the series on each inf ramarginai 

 plate is greatly enlarged and much more conspicuous than in the 

 young. In consequence of these changes, the general facies of 

 the adult is entirely different from that of the young, and if one 

 compares an adult specimen with Sladen's® figures, it seems 

 incredible that the two are really the same species. 



This seems to be a common species in water of moderate depth 

 off the coast of New South Wales, and the adult specimens were 

 identified, twenty years ago, by Mr..Thomas Whitelegge'^ as Astro- 

 2yecten triseriatus M. & T. As they do not have three series of 

 spines (or tubercles) on the superomarginal plates, they cannot 

 be that species, and it is fortunate that the "Thetis" collection 

 enables us to determine what they really are. Specimens labelled 

 " Astroi^fcten triseriatus, M. & T." have been sent out in exchange 

 by the Australian Museum, and it is therefore important to call 



8 Sladen— Chall. Report, Zool., xkx., 18S9, PI. xxxiii., figs. 3-4. 



9 Whitelegge— Journ. Koy. Soc. N.S. Wales, xxiii., 1889, p. 200. 



