490 ECHINUS AXGULOSUS. 



greater number of coronal plates, and structure of abactinal system, at once 

 separate this from E. miliaris. We have in the median interambulacral space 

 one principal vertical row of tubercles, but they are as small as the sec- 

 ondaries in E. miliaris; in the remainder of the plate they are arranged 

 irregularly, forming neither vertical nor horizontal lines, more closely packed 

 between the main row and the poriferous zone; towards the median line 

 the secondaries and miliaries occupying the coronal plate arc most numerous. 

 The arrangement is the same in the ambulacra! space ; the median vertical 

 rows are composed of small secondaries scarcely larger than those forming 

 the vertical line in the poriferous zone. The poriferous zone is much 

 broader than in E. miliaris, and there are from one to three indistinct vertical 

 rows of tubercles formed from the small secondaries. 



The differences in the anal systems of the two species are marked, the 

 genital ring is narrow, and frequently two of the ocular plates reach the 

 anal system, which is comparatively much larger than in E. miliaris; the 

 ocular plates are also larger. The secondaries on the genital plates near the 

 anal edge are small, and the anal plates are but little tuberculated ; both 

 in miliaris and in this species there are three to four very much larger anal 

 plates, — the rest are small, diminishing in size towards the anal opening; 

 actinal cuts more marked than in miliaris. 



The buccal membrane is thin, and is hut sparsely covered by limestone 

 plates, which, in this species and in Magellanicus, are reduced almost to a 

 minimum ; although E. angulosus belongs strictly to Psammechinus, the 

 plates are not even as numerous as Ave find them in Echinus proper. This 

 shows that the features upon which these two genera have been separated 

 are not tenable. In fact, when we examine young E. esculentus, it would 

 puzzle us to know whether to place them in Psammechinus, on account of 

 their close uniform tuberculation, or in Echinus, on account of their smooth 

 actinal membranes. 



Cape of Good Hope ; Mauritius ; Red Sea ; Philippine Islands ; New Zealand. 



