BIHANG TILL K. SV. VET.-AKAD. HANDL. 15AN1) 13. AKD. IV. N:0 O. 131 



From this it will have been seen that, allowanee made 

 for one single word of no great moment, the diagnosis and 

 descriptiou of tlie Ecliiuus saxatilis L. closely agree vvith the 

 rharacters exhibited by the youug of Diadema setosum Gray, 

 a species of wide distribution and from old time verv common 

 in collections. To that species therefore, and to no other, it 

 bclongs to bear the Linnean name, as Diadema saxatile L. 



Reverting now to the supplemcntal lines intercalated be- 

 tween Testa and Ambulacra, they bear like the rest of the 

 description the marks of having been first written down under 

 tlie E. Diadema and then, mutatis mutayidis, somewhat abridged 

 vmder the E. saxatilis. They have all the appearance of ha- 

 ving been drawn up subsequently to the completion of the 

 regular description and with the view of bringing forward the 

 ( lose allinity betvveen these two species as members of a division 

 of their owu, distinct from the rest. With the exception 

 of the term »convexi» used of the »radii^ in the E. Diadema, 

 but left out in E. saxatilis, their distinctions are hardly men- 

 tioned, while their resemblances are fullv indicated. The 

 »ambulacra quina lanceolata areis elevatiora» of the E. Diadema 

 are here termed »radii , and the same term is applied also to 

 the ambulacra dena, paribus approximatis» of E. saxatilis. 

 \ow it is worth remarking that Linn.eus counts five ambii- 

 lacra in all the Irreoulares, but ajnong the Reoulares onlv in 

 E. Diadema and E. Cidaris; that the word »radii» is met with 

 nowjiere else among the lleo-ulares, while amono- the Irregu- 

 lares it is invariably made use of to designate what we call 

 tlie petals; tliat the term »puncta perforata» applied to the 

 »lladii» ol" the Spatangi, the E. Spatagus and E. lacunosus, 

 is found also in the remarks on the radii» of the E. saxatilis, 

 while the strictly proper expression: »pori», occurs in the re- 

 gular description lower down; and that the term »centrum» 

 is used nowhere else amono- the lieoulares, but in the Irreou- 

 lares everywhere for the same part. Moreower, while nothing 

 like the whole insertion is found in any of the Regulares, its 

 contents are disposed in close accordance with the descriptions 

 of the Jrregulares, namely under the heads: stipra, centrum, 

 radii, and subtiis. 



It caunot be imagined that Linn.rus had the least idea 

 of the fact that the pedicels of the »five radii» in the Diade- 

 matida^ aud those of the Spatangi, by means of a peculiar 



