JAPANESE ASTEROIDEA. 271 



abactinal membrane passes and more or less aborted paxillar spinelets ; 

 beneath the membrane lies tlie terminal tentacL), there being no completion 

 of the calcareous ring on its abactinal side. In the larger example from 

 this locahty, tliin, narrow, calcareous connection is developed, on the floor 

 of the fuiTow, but only at the distal extremity of the plate, forming there 

 a dehcate arch over the terminal tentacle. Tliis division of the terminal x)late 

 is full of significance as regards the formation of tliis so-called single plate. 



" Variation. — In the specimen from Station 203 there is a small amoimt 

 of variation which is worthy of notice, although it might readily be passed 

 over. This occm^s in the armatm'e of the adambulacral plates, in prominent 

 robust thmnb-hke spinelet on the aboral margin of the plate being wanting 

 (see PI. XVm. fig. 2). The largest example is smaller than that from 

 Hong-Kong, hence it is possible that the ' thumb ' may be developed only 

 after full maturity is attained. On the other hand it may be said tliat as tlie 

 example under notice measm-es 11 = 37.5 mm., r = 9.75 mm., and has exactly 

 the same number of marginal plates (thirty-one, exclusive of the terminal) 

 as the larger Hong-Kong sxjecimen, its normal adult characters may be 

 considered to be present. 



" On comparing the two forms it may fm'ther be remarked that the 

 fm-row series of spines on the adambulacral plates are comparatively longer 

 in the specimens from Station 203, and also that the breadth of the ad- 

 ambulacral plates in relation to their length is slightly greater. The 

 marginal spines are comparatively longer and narrower, and they are 

 frequently pointed and channelled along their length, or gouge-sliaped. 

 The spinelets in the webbed fringe or the tln-ee attingent sides of the 

 adambulacral plates are fewer in number, as also are the spinelets on the 

 paxiU?e of the abactinal area (see PI. XVHI. fig. 1). These, however, are 

 characters which I regard as attiibutable to the smaller size. 



" Localities. — Cliallenger Expedition : 



"Hong-Kong, 10 fathoms. 



" Station 203, East of Panay Island (Philippine Group). October 31, 

 1874. Lat. 11° 6' 0" N. ; long. 123° 9' 0" E. Depth 20 fathoms. Mud. 

 Sm-face temperatm'e 85°.0 Fahr. 



