146 ECHTXOIDEA. 



Key to the Species. 



A. Primary spines very much longer than secondary. 



I. Mouth of moderate size. 



a. No red patches near periproct 1. E. acutus. 



(3. Red patches near periproct 2. E. norvegicus. 



II. Mouth very small 3. E. microstoma. 



B. Primary spines short. 



a. With purple tips 4. E. miliaris. 



j3. With tips not purple 5. E. esculentus. 



C. Primary spines moderate 6. E. elegans. 



1. Echinus acutus. 



Echinus acutus, Lamk. An. s. Vert. iii. (1816) p. 45 ; de Bl. Diet. 

 Sci. Nat. xxxvii. (1825) p. 78; Desmoulins, Syn. Ech. (1837) 

 p. 270 ; Aq. $ Desor, Ann. Sci. Nat. vi. (1846) p. 365 ; Aradas, 

 Atti Ac. Gioenia, viii. (1853) p. 276 ; A. Ag. Rev. Ech. (1872) 

 p. 121, & (1873) p. 489 ; Ludwig, Mitth, zool. Stat. Neap. i. (1879) 

 p. 558 ; Koehler, Ann. Mus. Marseille, i. 3. (1883) p. 121 ; Cams, 

 Prod. Faun. Mediterr. (1884) p. 100 ; Bell, Ann. $ Mag. iv. (1889) 

 p. 439 ; Prouho, C. R. cii. (1886) p. 444. 



Echinus miliaris, Flem. Mem. Went. Soc. ii. (1818) p. 246 ; Brit. 

 Anim. (1828) p. 478 [non anctt,]. 



Echinus flemingii, Forbes, Brit. Star/. (1841) p. 164; Dub. $ Kor. 

 Vet.-Ahad. Hdlg. 1844 (1846), p. 266; Ag. $ Desor, Ann. Sci. 

 Nat. vi. (1846) p. 365 ; Gray, Brit. Rad, (1848) p. 3 ; Sars, Nyt 

 Mag. x. (1859) p. 55; Grube, Insel Lt'ssin, (1864) p. 101 ; Wyv. 

 Thomson, Phil. Trans, clxiv. (1874) p. 744, pi. 68, fig. 14. 



Primary spines much larger and longer than secondary, more or 

 less pointed at their tip ; pale yellow in colour, but rather darker at 

 the base ; shorter, blunter, and more closely packed below than 

 above the ambitus. Secondary spines much more numerous, much 

 shorter and finer than the prirqary; the smallest exceedingly fine. 

 Pedicellariae very numerous, of various sizes, as much as 3 mm. in 

 length. The spines of the adult are proportionately shorter than 

 those of younger specimens. 



Test of full-grown form conical above, almost fiat below, small 

 mouth, moderately sized apical area ; neither primary nor secondary 

 tubercles are very numerous above the ambitus ; below, however, 

 the plates are well covered. Apical area pentangular ; periproct 

 rather large, all the radials shut off from it ; the madreporite is 

 not prominent, and the tubercles on the interradials are rather 

 small. In the interambulacra there about fifty plates, each of 

 which may, above the ambitus, carry one large primary tubercle ; 

 this may be very prominent or less well marked or absent ; below 

 the ambitus there are three or four subequal primary tubercles, and 

 these diminish in size and number as the mouth is approached. 

 The number of secondary tubercles is not large, and the miliaries 

 are not closely packed. The number of compound ambulacral 

 plates may be nearly fifty; each of these has a large primary 

 tubercle set about the middle of each plate, but the ambulacral 

 present the same kind of variations as the interambulacral tubercles; 

 above the ambitus secondary tubercles are very rare, so that in both 

 ambulacral and interambulacral areas the middle line is almost 



