324 



MR. W. PERCY SLADEN ON THE 



conical and pointed, and the companion one little more than 

 one fourth the length, cylindrical and obtusely tipped. The 

 large robust spine stands perpendicularly, and the small papilla 

 is usually directed at an angle towards the furrow and adorally. 

 On the outer surface of the plates near the base of the ray, espe- 

 cially in large examples, there may be one or two similar papilla ; 

 but I do not consider them sufficiently important to rauk as a 

 third series. 



The mouth-plates are elongate and narrow, with a single row 

 of eight to ten short, robust, conical spinelets on their surface, 

 which are very small outwardly, but increase in length as they 

 approach the mouth, the innermost spine being longer than any 

 of the others and directed horizontally. On the free margin of 

 the mouth-plate there is a lineal series of short, rather robust 

 spinelets, directed horizontally, which increase in length as they 

 approach the inner extremity of the plate ; the innermost spinelet, 

 being very little shorter than the innermost spinelet of the super- 

 ficial series above-mentioned and standing on the same level, 

 forms with it the horizontal fan of mouth-spines which proceeds 

 from each mouth-angle and covers the mouth. 



The madreporiform body is small, and situated at about its own 

 diameter distant from the margin. 



Colour in alcohol, a light shade of chocolate-brown, or an ashy 

 grey, in the latter case being lighter. 



Remarks. This species is the most nearly related to Astro- 

 pecten javanicus, Liitken, from which, however, it may be dis- 

 tinguished by the narrow marginal plates, by the character of 

 the adambulacral armature, and by the spinulation of the infero- 

 marginal plates. The facics of the two forms is quite different, 

 although, from its general structure, I am inclined to think 

 thai A. Andersoni is probably a descendant oi A. javanicus, or of 

 8 common ancestor, modified by isolation and changed conditions 

 of existence. 



2. ASTBOPEOTEN 1 1 BMPEIOHII, Miiller Sf Trosnhel. 

 Attropecten Qemprichii, Midler § Troschel, 1842, System der Asteriden, 

 P. 71. 



? Astropeoten artieulatus, Michelin, 1845, Essai d'une Faune de Vile 

 Maurice, May. de Zool. 2 C serie, 7 e annee, p. 24 (non Asterias articulatus, 

 Say, 1825). 



A tropeeten mauritianut, M&HuS, 1881, Beitr. z. Meeresfauna d. Insel 



Mauritius, p. bO (non Attropecten manritianui, (tray, 1840). 



