200 THE VOYAGE OF H.M.S. CHALLENGEK. 



with membrane, rather widely spaced, and usually no definite order of arrangement is 

 discernible, although about two irregular rows may be traced in some instances. 



The spinelets on the actinal intermediate plates are similar in character and disposition 

 to the foregoing, and they merge imperceptibly into the squamules of the infero-marginal 

 plates. This uniformity in the dermal appendages imparts a characteristic appearance to 

 the actinal aspect of the starfish. 



The mouth-plates are elongate, each with two short, flattened, truncate spinelets at the 

 inner extremity, followed by about six pairs of short robust spinelets, which stand per- 

 pendicular on the surface of the plate, and form two series apposed to one another ; these 

 are succeeded by about four rather broader, shorter, and more robust spinelets, forming a 

 single series in continuation, as it were, of the two apposed series, on the outer extremity 

 of the plate, towards which the spinelets decrease as they proceed outward. Consequent 

 on this method of arrangement there is a marked division of the mouth-plate armature 

 into two narrow series separated by the median suture line of each mouth-angle. 



The madreporiform body is small, and situated at about one-third of the distance 

 from the margin to the centre of the disk. 



The terminal (ocular) plate, though small, is conspicuous and elongately oblong. 



Colour in alcohol, umber-brown, becoming lighter in shade towards the extremities of 

 the rays. The spinelets are white. Small specimens are yellowish white. 



Young Phase. — A sm all example, which has a major radial measurement of 16"5 mm., 

 may readily be distinguished as belonging to the species. It is to be noted, however, that 

 the paxillaa of the abactinal area have quite a different character, the spinelets of the 

 crown being long, and radiating nearly horizontally. The armature of the adambulacral 

 plates and mouth-plates is comparatively longer, especially on the latter ; and on the 

 actinal surface of the adambulacral plates behind the furrow series there are usually one 

 or two larger spinelets, thickly invested with membrane, especially noticeable on the inner 

 part of the ray, but of which no trace remains in the adult — that is to say, their prominence 

 and juvenile robustness are altogether lost. 



Locality. — Station 232. Off the coast of Japan, south of Yeddo. May 12, 1875. 

 Lat. 35° 11' 0"N., long. 139° 28' 0" E. Depth 345 fathoms. Green mud. Bottom 

 temperature 41°'l Fahr. ; surface temperature 64°'2 Fahr. 



Remarks. — Astropccten brevispinus is distinguished from the other species in this 

 section of the genus Astropccten by the single lateral spine, by the character of the 

 adambulacral armature, and by the character of the paxillse. It differs from Astropccten 

 antillensis and Astropccten brasilicnsis in each of these particulars. It is at once dis- 

 tinguished from Astropccten aurantiacus, which Las a single lateral spine, by the general 

 facius, and by the character of the adambulacral armature ; and from Astropecten crinaceus 

 and Astropccten dvplicatus by the single lateral spine and the different character of the 

 spinulation of the infero-marginal plates. 





