410 CENTROSTEPHANUS CORONATUS. 



difference in the ocular plates, which are far broader and more elongated 

 laterally in C. Rodgersii than in C. coronata, where the ocular plates are 

 nearlv hexagonal. Another very important difference is shown by the 

 spines, which, as far as I have observed, in Echinothrix. in Astropyga. and 

 in this genus, oiler good specific differences. We will leave out of question 

 their greater proportional length in ('. coronata. on account of the differ- 

 ence in size, and simply compare the verticillatious : we find in C. coronata 

 the whirls very large and very distinct, the height of two whirls being 

 equal to the diameter of the spines, while in C. Rodgersii five whirls arc 

 equal to the diameter of the spines; the whirls are also much less regularly 

 arranged, the spines often appearing striated longitudinally in consequence; 

 the verticillation being very slightly prominent. A similar structure exists 

 in older spines of C. coronata; there are sixteen longitudinal lines in C. 

 coronata, only eleven in C. Rodgersii. Actinal cuts more marked in Rod- 

 gersii; hut this is a feature which, having developed with increasing size, 

 can scarcely he taken into account. 



The following is the description of a small specimen of this species as 

 given by Professor Verrill, in his Notes on Radiata, page 295. 



-Te<t circular, much depressed; actinal opening one half the diameter 

 of test, with very slight cuts, its membrane partially covered by five 

 principal groups of large oblong scales, which support numerous slender, 

 somewhat clavate spines. .1 inch long, and numerous short, rounded pedi- 

 cellate. Ambulacral pores large, in arcs of three pairs, becoming more 

 oblique below, where the zones are wider; tubercles in two lows, rather 

 large, with a median zigzag line of miliaries. Interambulacra about twice 

 as wide as the ambulacra, with two rows of tubercles, somewhat larger than 

 those of the ambulacra, reaching the abactinal region : external to these 

 are two irregular rows of small tubercles bordering the ambulacra; and 

 between them two imperfect rows of about the same size, arranged alter- 

 nately, with smaller miliaries scattered among them. The three uppermost 

 tubercles of both the ambulacra! and interambulacral system are very small, 

 and the two next the last bear small slender spines with globular, bright 

 purple tips. The ocular and genital plates bear each a somewhat longer, 

 slender spine. Abactinal system small, somewhat angular, depressed ; spines 

 twice as long as the diameter of the test, rather stout, with conspicuous ver- 

 ticillations, annulated with narrow bands of purplish-brown and light brown. 

 Diameter of test 0.85 of an inch ; height, 0.35. 

 Cape St Lucas. 



