ECHINUS MAGELLANICUS. 11 



the actinal side of Coelopleurus {Figs. 4, 5, e), while it develops into the 

 long, hooked, curved spines {Fig. 7) of the ambulacral system on the abac- 

 tinal side of the test, as well as on the lower interambulacral spines nearest 

 the actinostome. In the Arbaciae this appendage remains a sort of cap only 

 on the spines of the actinal side, and is not developed on the spines above 

 the ambitus, as is the case also in most of the serrated interambulacral spines 

 above the ambitus. 



The anal system is covered by four anal plates of slightly unequal size ; 

 in larger specimens the anal edge of the plates carry small granules and 

 minute secondaries, while in smaller specimens the plates are smooth or 

 very minutely chagrined. Fragments of the test, dredged off the Barbadoes, 

 show that this species must have attained a diameter of at least an inch and 

 a quarter. 



100 fathoms, off the Barbadoes. 



Echinus magellanicus 



! Echinus magellanicus Fun.., 1857, Wieg. Archiv. 



PL IILf.S. 



A large number of specimens were collected at different points through 

 the Straits of Magellan. The denuded test figured on PI. IILf. 5, shows the 

 great similarity of this species to E. microtuberculatus from the Mediterra- 

 nean ; like it, the South American species does not appear to attain as large 

 a size as the more northern E. miliaris. 



Lat. 37° 42', South ; Long. 56° 20', West. 



Straits of Magellan ; Magdalena Islands ; Eden Harbor ; Sandy Point ; Shoal Bay. Lat. 4D° 40', 

 South ; Long. 66° 50', West. 57 fathoms. 



Echinus margaritaceus 



! Echinus margaritaceus Lam., 1816, An. s. Vert. 



PI II. f. e; PL IILf. 4. 



A figure of the large specimen described in the Revision of the Echini 

 (Part III. p. 493) is given on PL II. /. g. A good series of various sizes was 

 collected by the Hassler Expedition, at different points along the southern 

 extremity of South America. The changes due to growth are similar to 

 those observed in E. norvegicus, to which this species is most closely allied. 

 A younger specimen is also figured in PI III./. 4, showing satisfactorily that 

 E. magellanicus cannot be the young of E. margaritaceus, as the latter has, 

 when not more than half the size of the former, a larger number of primary 

 interambulacral tubercles. 



