EEPORT ON THE ECHINOIDEA. 63 



few secondary and miliary ones ; only in the region near the ambitus and towards the 

 actinal area do the small primaries occupy the whole of the interporiferous zone towards 

 the abactinal region. Near the actinal region in the last four or five plates of the 

 ambulacral area there are, in the angles of the plates along the median fine, deep elliptical 

 pits (PI. VI. fig. 7), of the size of the larger ambulacral pores, in which sphseridia are placed. 



In the ambulacral area the tubercles are small, placed upon a prominent boss rising 

 sharply from a broad flat distinct scrobicular area (PI. VI. fig. 5). The poriferous 

 zone is broad, the pores large, forming more or less distinct arcs of three pairs round the 

 base of the primary tubercles (PI. VI. fig. 5) near the equatorial region of the test. The 

 pores become smaller, and are placed closer together towards the ambitus (PI. VI. fig. 7) ; 

 they are still smaller on the actinal surface. There is no tendency at the very edge of 

 the actinal opening towards the petaloid structure so prominent among other Arbaciadse 

 (PI. VI. figs. 3, 7, 8, 10, 11). In the interambulacral spaces there are not more than 

 from seven to eight primary tubercles, corresponding in size, except the last two upper 

 ones (PI. VI. fig. 6), to the adjoining ambulacral primaries ; they are also separated 

 along the median line by a few secondaries and miliaries. On the last five or six 

 interambulacral plates towards the abactinal region there are no primary tubercles, the 

 whole median space is bare (PL VI. figs. 1, 2, 6, 9a, 13) with the exception of the three or 

 four smaU secondary tubercles placed near the outer edge of the plates, and which, in the 

 other plates carrying primary tubercles, separate them from the poriferous zone. This bare 

 median interambulacral space is ornamented by a few flat, broad, inconspicuous miliaries, 

 and by smooth broad bands, somewhat raised (PL VI. fig. 6), forming ii-regular S-shaped 

 lines extending from the centre of one plate to the upper edge of the following plate 

 (PL V. fig. 1). A brilliant carmine band extends from the genital ring on the inner edge 

 of the secondary tubercles, separating the poriferous zone from the bare space. These 

 secondary tubercles are reduced in number as they approach the genital ring. The 

 genital ring (PL VI. fig. 4) is narrow, the anal edge is somewhat raised by a ring formed 

 of broad flat indistinct miliaries, the outer portions of the genital plates being smooth ; the 

 genital plates are connected, surrounding the ocular plates which are crescent-shaped, 

 smooth, with one or two diminutive notches, and with a slight hood-like cap over the 

 odd terminal tentacular opening. 



The genital openings are large, placed near the outer edge, with the exception 

 of the opening on the madreporic genital which is on the edge of the plate, the mad- 

 reporic body occupying its central portion (PL VI. fig. 4). There are four large smooth 

 anal plates. The genital ring and ocular plates are of a vivid carmine, similar to the 

 vertical interambulacral bands. The actinal notches are not deep, but the grooves formed 

 by the lips for the attachment of the angular prolongation of the actinal meml^raue 

 covering the passage of the gills are quite prominent (PL VI. fig. 7). The pi-incipal 

 difierences in smaller specimens consist in the proportionally greater width of the 



