14 SALEXIA PATTERSON! 



like spines found near the actinostome. The papillae or secondary spines are 

 long, with a rounded slightly concave extremity. The outer edge of the abac- 

 tinal system and the median line of the ambulacra! area are thickly studded 

 with minute globular pedieellariae. The plates of the abactinal system are 

 covered by a coarse granulation ; this towards the outer edge of the geni- 

 tal plates becomes minute sessile spines. The sutures between the genital 

 plates, as well as the lines separating them from the abactinal part of the 

 ocular plates, are deep. The anal system carries short, stout, pointed spines. 

 None of the genital pores, with the exception of the madreporic genital, are 

 very distinct ; the madreporite consists of a few minute pores adjoining the 

 large genital pore. The ocular plate opposite the superanal plate nearly 

 touches the anal system, approaching it much closer than is the case in 

 IS. I'arisjrina. 



In specimens measuring 12 mm. in diameter, there are usually from five to 

 seven primary tubercles in the interambulacral area. The secondary tuber- 

 cles, carrying the flat papillae, are arranged vertically in open arcs round 

 them; and these arcs, running together along the median interambulacral 

 line, form two wavy vertical rows of tubercles, closely packed, which gives 

 to the median interambulacral area a somewhat sunken aspect, as in Go- 

 niocidaris. The ambulacra! tubercles, as in S. varispim, resemble in their 

 arrangement those of Hemicidaris, forming two vertical rows ; they are 

 largest near the ambitus, diminish rapidly in size towards the actinostome, 

 and more gradually towards the apical system. The largest ambulacra! 

 tubercles are not larger than the secondaries surrounding the primaries of 

 the interambulacral area. The ambulacral zone is narrow; the pores are 

 arranged in a slightly undulating line, following irregularly the outline of the 

 primary plates in the interambulacral area. Smaller and larger specimens 

 differ only in the size of the primary tubercles, those towards the actinos- 

 tome increasing but slowly in size as the diameter of the test enlarges. The 

 principal differences to be noticed are in the greater number of imbricating 

 plates which cover the actinal membrane in the older specimens, as compared 

 with the more simple arrangement of (he plates and their smaller number in 

 earlier stages. In younger specimens the live pairs of large buccal tentacles 

 cover nearly the whole actinostome; they nexl become separated from the 

 actinal edge of the tot by ;l few irregularly arranged imbricating plates, and 

 as the rows of plates increase they form also narrow zones between the pairs 

 of buccal plates ill extension of the interambulacral areas, until in the older 



