j56 echinoidea. i. 



The globiferous pedicellariæ witli the edges of the blade 

 thickened, connected by cross-beams across the inside (in 

 Ech. Alexandria however, sonietimes without such cross- 

 beams) 5. 



4. The piates on the buccal membrane thick, greenish, of a 

 peculiar structnre (a compact calcareoiis mass with deep, 



funnel-shaped holes); they form a dense covering Parcchinus microtiiberculafns (Blv. 



The piates on the buccal membrane not greenish, of 

 the common structnre; they form uo quite dense covering, 

 naked skin is seen between them Parechinus miliaris (Miill.). 



5. Primary tubercle on all the ambulacral piates 6. 



— — only on every other ambulacral plate... 11. 



6. The tridentate pedicellariæ with the blade broad and rather 

 flat; the globiferous pedicellariæ generally with 3—4 teeth 



on either side of the blade Echirius Alcxandri Dan. Kor. 



The tridentate pedicellariæ with the blade narrow and 

 deep; the globiferous pedicellariæ with 1--2 teeth on either 

 side of the blade 7. 



7. The primary tubercles on the ambulacral areas of ver}" 

 unequal size, or, if the size decreases regularly towards the 

 apical area and the peristome, the two series in each 



ambulacral area of very different size Echinus affinis Mrtsn. 



The primary tubercles on the ambulacral areas decrease 

 regularly in size towards the apical area and the peristome; 

 both series of equal size 8. 



8. The test high 9. 



— rather flat 10. 



9. Finely red; the ophicephalous pedicellariæ with uncom- 



monl)- long blade Echinus atlanticus Mrtsn. 



With a fine green coloration; the ophicephalous pedi- 

 cellariæ of the connnon form Echinus gracilis Ag. 



10. The globiferous pedicellariæ generally with 2 — 2 lateral 

 teeth; the test and the spines generally finely red and 



white, more rarely the test violet Echi?ms elegans Diib. Kor. 



The globiferous pedicellariæ generally with i — i lateral 

 tooth; the test and the spines white Echinus lucidus Doderl. 



11. Spines on the buccal piates; the primary spines short, 



thick, not distinctly longer than the secondary ones Echirius esculenttis L. 



No spines on the buccal piates; the primary spines 

 considerably longer than the secondary ones 12. 



