GONIMARETIA TYLOTA. 241 



Key to the Species of Gonimaretia. 



Test wide and flat, the width nearly .90 length, the height much less than .45 length; 3 



large primary tubercles in each of interambulacra 1 and 4, near ambitus tylota. 



Test narrower and higher, width .80-.85 length and height about half length; no primary 

 tubercles on dorsal surface. 



Petals I and V much wider proximally than distally; posterior end of test vertically 



truncate, not overhanging laevis. 



Petals I and V of nearly uniform width; posterior end of test obliquely truncate and 



overhanging inlerrupta. 



Gonimaretia tylota, sp. no v. 1 



The only available specimens of this species are from the Challenger 

 collection. The one selected for the holotype (M. C. Z. Cat. no. 3208) is 31 mm. 

 long, 27 mm. wide and not quite 14 mm. high. A slightly larger specimen is 

 relatively wider and natter, 33 mm. long, 30 mm. wide and 14.5 mm. high. 

 The figures in the Challenger Report (PI. 37, figs. 1-4) give a good idea of 

 the appearance of the specimen with spines on (fig. 1) and of the general appear- 

 ance of the bare test. But the figures are all enlarged about twenty per cent 

 and the relative proportions are not perfectly exact. The petals are not very 

 successfully reproduced. Petals I and V are in their general form like petal V 

 in fig. 6, PL 161, but are decidedly narrower; they are about 12 mm. long, 

 3 mm. wide proximally and almost pointed distally; in the outer series of pore- 

 pairs, there are 22 or 23 of which the basal 5 or 6 are extremely small and can 

 hardly be made out; in the inner series, there are 21 pore-pairs of which the 

 basal 7 can hardly be made out. Petals II and IV are even more different 

 from the Challenger, figure. They are notably unequal and this asymmetry 

 is shown in all four of the specimens before me. Petal II is about 9 mm. long 

 (in the holotype) and has 14 pore-pairs in the posterior series, all but the basal 

 two being large and easily seen; in the anterior series are approximately the 

 same number of pore-pairs, but only the 4 or 5 at the tip of the petal are visible 

 and these diverge from the posterior series at an angle of about 40°. Petal IV 

 is about 11 mm. long and there are 17 pore-pairs of which 15 are conspicuous. 

 The apical system is very compact and there are large genital pores in genital 

 plates 1, 3, and 4; there is no pore in 2. Ambulacrum III is not at all petaloid 

 and is not sunken in the least; the pores are small and the plates are not easily 

 distinguished. Just anterior to the apical system on each side of ambulacrum 



1 Tv\urr6s = knobbed; in allusion to the knob-like primary tubercles on each side. 



