JAPANESE ASÏEEOIDEA. 49 



plates. The outer series of ventrolaterals consists of two or three 

 very small plates ccnfined to the inner side of the first infero- 

 marginals ; they may bear a few exceedingly small spines. The 

 pectinate pedicellarise which are characteristic of this genus are 

 found between the first and second plates of the inner series of 

 ventrolaterals, either one on either side or only one in an inter- 

 radius. Each pedicellaria consists of 4-6, somewhat flattened, slight- 

 ly curved spines, about a millimeter in length, situated on the 

 margin of the first ventrolateral turned towards the second ventro- 

 lateral plate, and about as many spines on the latter projecting 

 against the spines of the first plate, the spines of the two plates 

 alternating with one another. Without seeing a live specimen it 

 is hard to say how these spines act during life, but the propriety 

 of applying the name of pedicellaria to them appears to me open 

 to doubt. In all the Phanerozonia I have examined, the pedicel- 

 laria is accompanied by a small hole in the plate, which gives 

 exit to the muscle fibres from the subjacent tissue to the base of 

 the pedicellaria -valves ; so that even after the pedicellarisß have been 

 abraded, their presence can be detected by means of the small 

 holes left in their places. Moreover the valves of a pedicellaria 

 always belong in other forms to the same plate. Now in the case 

 of the pectinate pedicellarise of Cheiraster these two characteristics 

 do not apply, the constituent spines belong to diflferent plates and 

 they do not leave any hole after them, showing that the muscle 

 fibres, which are no doubt present around the bases of the spines, 

 must be merely superficial and do not pass out from the deeper 

 layer, as in the typical pedicellariae. As mentioned above these 

 pectinate pedicellarias are also present sometimes on the infero- 

 marginals, and in such a case the plates may be so far apart 



