428 MR. W. p. SLADEN ON THE ASTEHOIDEA 



with the spines upon the dorsal marginal plates. On the speci- 

 men under consideration these are so small that they might 

 easily be passed over without notice, — whilst, further, it is a cha- 

 racter of such usual variability that I am fully prepared to believe 

 in the existence of examples in which they are wanting altogether, 

 their rudimentary state on the present specimen quite leading to 

 that idea. A seemingly parallel instance may be pointed to in 

 the case of Astr. eury acanthus, Ltk.*, in the premature stages of 

 which small spines are present on the outer margin of the dorsal 

 marginal plates towards the ends of the arms, but no trace of them 

 remains in the adultf. 



Our knowledge of this species at present is very scanty ; and 

 it may not be beyond the range of probability that a more exten- 

 sive series of specimens will require the modification of our 

 current ideas of the form altogether, and possibly even its amal- 

 gamation with such a species as A. sco2^arius, when more is defi.- 

 nitely known about the premature stages of these Astropectens. 



AsTEOPECTEN poLYACANTHus (of A. annatus-tjTpe), M. Sf T. 



1842. Astropecten polyacanthus, Miiller ^ Troschel, System der As- 

 teriden, p. 69, taf. v. fig. 3. 



— Astropecten hystrix {Val. MS.), M. Sf T. ibid. p. 70. 



— Astropecten armatus, Miiller ^ Troschel, ibid. p. 71- 



1843. Astropecten vappa, Miiller fy Troschel, Wiegm. Archivf. Natur- 

 gesch. Jahrg. 9, p. 119. 



1864. Astropecten armSitus,Liitken, Vidensk. Meddelelser for 1 864, p. 132. 



1865. Astropecten armatus, v. Martens, Ueb. Ostasiat. Echin., Wiegm. 

 Archiv, Jahrg. 31, p. 352. 



18/6. Astropecten polyacanthus, Terrier, Stell. du Mus., Arch, de Zoo- 

 logie gen. et exper. t. v. p. 275. 



Coll. St. John : Tedo Bay. 



So far back as 1864, Dr. Liitken % raised the question as to the 

 validity of the separation of A. armatus, M. & T., from Japan, and 

 A. vappa, M. & T., from Australia, as species distinct from the 

 typical form of A. polyacanthus from the Red Sea, asserting his 

 inability to detect in the material he had examined any characters 

 of specific value to warrant such a division. M. Perrier, after 



* Vidensk. Meddel. 1871, p. 232. 



t Compare with this Liitken's remarks on a specimen of Astr. aster wanting 

 the spines (in Vidensk. Meddel. 1864, p. 130). 



X " Kritiske Bemaerkninger om forskjellige Sostjerner," Vidensk. Meddel. 1864, 

 p. 132. 



