126 SVEN LOVEN, ON THE ECHINOIDEA DESCRIBED BY LINN^US. 



used for the same parts in tlie Regulares. By this means 

 these two species are made to stånd out united, for themselves, 

 from among the others. 



No speciracn referable to the E. saxatilis exists in the 

 collection, and since its printed label is found lying at the 

 E. Liicnnter L., it is probable that it was löst before 1790. 

 Biit of the species set down as Echinothrix Turcarum by 

 Alexander Agassiz, there is a fine speciraen, Tab. 4, fig. 1, 

 2, 3, signed in Thunberg's hand: »Mus. Gust. Ad.», to indi- 

 cate its having come from the Queen's Cabinet. It is doubt- 

 less the type of the Echinus Diadema L. It will be found 

 convenient to take it into consideration previous to the other. 



The test of the E. diadema, says the description, is slightly 

 tumid all around the depressed centrum. The periproct is 

 nearly orbicular, slightly oval. The ambulacra, called radii 

 in the supplement, are not, as usual, ten in number, but five 

 as in the E. Cidaris. Thus the term »ambulacrum» is here made 

 to embrace not only the two zona? porifera?, but also the space 

 between every two of these, or Avhat Linn^us elsewhere calls 

 »area angustior> or »areola». This is the acceptation of the 

 term nqw in use. Dorsally the ambulacra are lanceolate, con- 

 vex and elevated above the interradia. Between thcir tAvo 

 lateral series of secondary tubercles, the middle space or di- 

 seus presents up to quadruple rows of tertiary tubercles. The 

 pedicellar pores are multiple, not forming a simple series, 

 and below, uear the peristome, arranged in diagonal rows 

 of six, that is of three geminous pores. On their outside, 

 the zones of pores are accompanied by a series of »larger» 

 tertiary tubercles, continued on the vmder side, but there less 

 regular: :;minus ordiuata», the word »subtus» taken as referring 

 solely to the »Puncta . . .;>, evidently not to the »Centrum . . .» 

 or the »Radii . . . >. On the interradia are scattered minute 

 tertiary tubercles, and the large primary tubercles form six 

 vertical rows, three on each half; they are conic, their scro- 

 bicular circles are smooth, not beset Avith small tubercles 

 round the margin like thosc of the E. Cidaris, and the ma- 

 melon is perforated. 



In the E. Diadema L. thus described, recent authors, as 

 Alexander Agassiz and Bölsche, Avho quotes the ]\I. L. U., 

 recognised a species of the genus Echinothrix Peters. The 

 perforated mamelon is decisive Avith regard to the family, while 



