CH^TODIADEMA PALLIDUM. 127 



The actinal plates of the ambiilacral area each carry only a single pair of 

 pores. At about the sixth (PI. 56, fig. Jt) plate from the actinostome, small 

 secondary plates are intercalated, forming compound plates with irregular 

 arcs of three pairs of pores. On the abactinal part of the test, except near 

 the abactinal system, and even below the ambitus, each such plate car- 

 ries a primary tubercle, perforate and crenulate, which completely obliter- 

 ates the sutures of the primitive plates. The arrangement of the pores on 

 the actinal face is thus quite different from that described by Mortensen 

 (1. c. p. 24).^ 



The whole abactinal part of the interambulacral area is nearly bare, the 

 upper six or seven plates carrying only a few iniliaries and small secondaries 

 adjoining the poriferous zone. There are six vertical rows of perforate and 

 crenulate primary tubercles, each row consisting of three, four or five tuber- 

 cles ; of the outer rows three primaries are above the ambitus and two below ; 

 of the inner row three (or two) below and two (or one) above; a fourth 

 row, between the outer two, is indicated below the ambitus by the presence 

 of one or two primaries. 



This species is readily distinguished from the two species hitherto known 

 by its color, which is pale buff when dry, more or less tinged with purple when 

 wet, becoming a buff white beneath. The sides of the bare interambulacral 

 areas on the abactinal surface are more or less distinctly yellow ; in many 

 specimens the ambulacral edge of this area is marked by a broad dull red 

 line extending from the ambitus to the genital plates (PI. 59, fig. 2), but 

 these lines may be interrupted, and in about half the specimens are entirely 

 wanting. There is no blue either on the test or spines, as in the figure of 

 Ch. granuiatiim given by de Meijere (PL XI, fig. 101). A similar band is 

 prominent in one of the figures of Ch. japoiiicum given by Mortensen (/. c. PI. 

 2, fig, 16). It is less distinct in Ch. gramilatiim (Mort., PI, 1, fig. 22). Some 

 of the individuals have on the actinal side a deep brown line, forming a more 



^ I would not venture to doubt the existence of the splitting of the actinal interambulacral plates 

 as observed by Dr. Mortensen or to intimate as he has done that the splitting of the actinal interam- 

 bulacral plates which I observed in Astropyga was probably due to rough handling of the specimens ; 

 or as he says, " and it is rather probable that the splitting up of the plates in large specimens may be 

 due simply to the breaking of the delicate plates by the handling of the specimens." This is but one of 

 the many instances of acidulous criticism and endless fault finding indulged in by Dr. ^lortensen. 

 He is constantly objecting to this or that figure as being bad. I would call his attention to the very 

 unsatisfactory figures he has given of Chcetodiadema granulatum and Ch. japonicum on Plates I, 

 figs. 1, 3, and II, figs. 16, 19 of his Siam Ex. Echini, and to the confusion he creates, far more 

 aggravating than anything he finds to correct, by his irregular numbering on the same Plate of 

 figures belonging to the same species (PL I, 1, 3, 21, 22 ; PI. 11, figs. 16, 19) ; his standard of con- 

 venience and of excellence is a most variable quantity. — A. Agassiz. 



