146 ECHTNOIDEA. 
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. 
8. Red patches near periproct .......... 2. E. norvegicus. 
IL, “Mouthivery sara en no ee ee ter 3. E. microstoma. 
B. Primary spines short. 
a. Withopurple tips oe ape ae Gir oe A. E. miliaris. 
8. With tips not purple i.e. en cette eck 5. E. esculentus. 
C. Primaryxspines moderate yy .ceie aoe ene 6. FE. elegans. 
1. Echinus acutus. 
Kchinus acutus, Zamk. An. s. Vert. iii. (1816) p. 45; de Bl. Dict. 
Sci. Nat, xxxvii. (1825) p. 78; Desmoulins, Syn. Ech. (1887) 
p. 270; Ag. § Desor, Ann. Sct. Nat. vi. (1846) p. 865; 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; Carus, 
Prod. Faun. Mediterr. (1884) p. 100; Bell, Ann. § Mag. iv. (1889) 
p. 439; Prouho, C. R. cii. (1886) p. 444. 
Kchinus miliaris, Flem. Mem. Wern. Soc. ii. (1818) p. 246; Brit. 
Anim, (1828) p. 478 [non auctt. ]. 
Kchinus flemingii, Forbes, Brit. Starf. (1841) p. 164; Diib. § Kor. 
Vet.-Akad. Halg. 1844 (1846), p. 266; Ag. & Desor, Ann. Sct. 
Nat. vi. (1846) p. 365; Gray, Brit. Rad. (1848) p. 3; ’ Sars, Nyt 
Mag. x. (1859) p. 55; Gr ube, Insel Lussin, (1864) p. 101 ; Wyo. 
Thomson, Phil. Trans. clxiv. (1874) p. 744, pl. 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 primary; the smaliest exceedingly fine. 
Pedicellarie 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 flat 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 
