468 MICROCYPHUS MACILATUS. 



specimens a totally different aspect from the adult or older stages. This 

 stage of growth I have called Anthechinus. The tuberculiferous portion 

 of the test is of a delicate green, while the hare spaces are of a light violet 

 tinge. The spines are long, slender near actinostome, of transparent green- 

 ish color, with one or two narrow dark green bands near the tip of the 

 spines. Above the ambitus they are shorter, tapering, with one or two 

 irregularly placed dark hands. The genital plates arc 1 hare except near the 

 anal edge, of a delicate yellowish-pink color. The ocular plates carry tuber- 

 cles, as in the older stages. 



In still younger stages, 13 mm- , the outline is more circular, though the 

 character of the test, as far as the arrangement of the tubercles is concerned, 

 in both areas is the same as in the specimen just described. The pits of the 

 horizontal sutures at the junction of the poriferous zone with the interainbu- 

 lacral space an' deep. The poriferous /one is quite narrow, pores arranged 

 in one regular vertical row. The pits of both areas are still more marked 

 in younger specimens, gradually becoming obliterated with increasing size, 

 first in the interambiilacral space, and afterwards in the ainhulacral space. 

 The poriferous zone changes gradually from a regular vertical row of single 

 pairs of pores to a slightly irregular one. then to a regular inner row with 

 an irregular outer one. which in the oldest specimens becomes a regular 

 outer row with a smaller number of pores than the inner one. In small 

 specimens the spines vary in color from a light yellow to a dark green, more 

 or less plainly handed, ami the spines of small specimens, ll"" n - in diameter, 

 are proportionally mucb longer above the ambitus than in the older stages. 

 Actinal membrane hare except the ten buccal plates. 



The variations in the pits and hare spaces in different stages of growth 

 show how little reliance can he placed upon their shape and extent as far 

 as specific determinations are concerned. Specimens of the same size, as 

 is also the case in Amblypneustes, either having very deep median pits or 

 pits reduced to mere rudimentary pores, while, as is well known in some 

 species of Salmacis, the sutural pores may become deep furrows, as promi- 

 nent as in any species of Temnopleurus. 



.Taprtn ; East India Island? : Navigator Islands. 



