Anatomy of the Temnopleuridge. 115 



and if their middle sutures were more curved, the arrange- 

 ment would be Diadematoid; but the adoral suture of the 

 upper and the aboral suture of the lower primary are nearly 

 transverse. Nearer the ambitus are some arrangements of 

 plates unlike any hitherto noticed. There is an upper 

 compound ambulacral plate (fig. 10) and the aboral com- 

 ponent is a long low primary (c) with its adoral suture dipping 

 towards the next plate in adoral succession. This plate {b) 

 is a small triangular one, and its adoral suture does not 

 reach the adoral yore of the pair belonging normally to the 

 plate. Under the use of evaporating benzule I cannot 

 detect any suture coming fi'om the adoral pore. Conse- 

 quently the adoral component (a) of the plate under considera- 

 tion is a large primary, and includes the adoral pore of the 

 pair properly belonging to the demi-plate above, hi the 

 compound plate next below, the upper component plate (c) is 

 the usual primary, and the next {b) is a demi-plate with its 

 suture passing fi'om the adoral pore of its pair vertically to the 

 corresponding or adoral pore of the pair of the primary above. 

 The dotted line is in the path of a thickening which recalls 

 the position of the suture in fig. 9. 



In the next plate (fig. 11) the suture of the adoral pore of 

 the middle plate [h) is plainly turned obliquely upwards 

 and outwards to reach the small demi-plate, and the first sta^e 

 of the exclusion of a pore from its plate is exemplified. 

 Fig. 11 is of two compound triple plates, and in the upper 

 one the aboral member is a low primary (c) ; the next plate 

 [b)j which should have been a perfect demi-plate, is one 

 which only contains the aboral pore of its pair, and is excluded 

 from the ambulacro-interradial suture. The adoral pore of 

 the pair {b) has its suture just touching the union of the 

 adoral suture of the single pore-bearing plate with the adoral 

 suture of the upper primary (c). 



The lowest plate (a) is a large irregular primary. The 

 same condition of things is seen in the next or actinal com- 

 pound plate (the lowest of fig. 11), but the aborted plate" (i), 

 -v\ith only one pore, is not excluded from the ambulacro-inter- 

 radial suture. Below the ambitus of the test the variety in the 

 distribution of the sutures, as seen from within under benzule^ 

 is as extraordinary as abactinally, for (fig. 12) in a well-marked 

 example the upper (c) component is a low primary with a dip 

 down of its adoral suture towards the space between the pores 

 of the middle {b) component plate, and the adoral pore has got 

 above and out of the touch of the adoral suture. The middle 

 pair of pores {b) has its aboral pore in a demi-plate ; but 

 the adoral pore is on the line of the adoral suture of the upper 



