ECHINOCARDIUM. 169 
1. Echinocardium cordatum. (Plate XVI. figs. 1-4.) 
Kchinus cordatus, Penn. Brit. Zool. iv. (1777) p. 58, pl. xxxiv. fig. 75 ; 
td. op. cit. iv. (1812) p. 139, pl. xxxvi. fig. 2. 
Spatangus arcuarius, Lamk. An. s. Vert. iii. (1816) p. 32. 
Kchinocardium pusillus, Gray, Ann. Phil. xxvi. (1825) p. 480. 
Spatangus cordatus, Flem. Brit. An. (1828) p. 480. 
Spatangus ovalis, van den Ende, Nat. Verh, Hollandsche Maatsch. xvi. 
2, (1828) p. 301. 
Amphidotus cordatus, Forbes, Brit. Starf. (1841) p. 190 ; Thompson, 
Nat. Hist. Irel. iy. (1856) p. 442. 
Amphidetus cordatus, Diib. § Kor, Vet.-Ak, Hdlg. 1844 (1846), 
p- 285; Ag. § Des. Ann. Sci. Nat. viii. (1847) p. 11, & vi. (1846) 
pl. xyi. fig. 8; Sars, Norg. Ech. (1861) p. 97. 
BKehinocardium cordatus, Gray, Brit. Rad. (1848) p. 6. 
Amphidotus arcuarius, Maitland, Faun. Belg. septent, (1851) p. 91. 
Kchinocardium cordatum, id. Cat. Ech. (1855) p. 45; Du. § Hup. 
Echin. (1862) p. 602; Al. Ag. Rev. Ech. (1872) pp. 109 & 349, 
pl. xix. figs. 10-17 & pl. xx. tigs. 5-7; Mob. § Bits. JB. Comm. 
Kiel, ii. & iii. (1875) p. 150; Ludwig, Mitth. zool. Stat. Neap. i. 
(1879) p. 561; Koehler, Ann. Mus. Marseille, i. 3. (1885) p. 180; 
Carus, Prod. Faun. Mediter, (1884) p. 102; Fleischmann, Zeit. f. 
wiss. Zool. (1888) p. 151 (development). 
Body irregularly heart-shaped, widest at its posterior third ; ante- 
rior ambulacrum in a rather deep groove, spines silky grey, none 
very long above; when the spines are well developed they con- 
siderably obscure the anterior depression, and the whole creature has 
a brownish hue. ‘The longest spines are the backwardly directed, 
slightly curved spines found on either side of the ventral surface ; 
the outermost on the plastron are curved outwards and backwards, 
but the greater number are a little shorter, stouter, and spatulate at 
their free ends. On the upper surface the most prominent spines 
are found just in front of the apex and on either side of the 
anterior ambulacrum, 
The test of a full-grown adult is only a little higher posteriorly 
than anteriorly, and the heart-like form is not very apparent. In 
smaller specimens, which are much more common, the hinder part 
is distinctly higher than the anterior and the cordiform shape of the 
test is much more pronounced. The hinder aspect descends verti- 
cally, and the anus is not overhung. 
The groove for the anterior ambulacrum is very well marked 
anteriorly, on the upper surface it forms a shallower depression ; 
the apical system is some distance behind the middle of the back ; 
the internal fasciole is symmetrical on either side of the middle line 
and is rather broader behind than in front; the number of well 
marked pairs of pores in the antero-lateral ambulacra are often 7 in 
the anterior and 11 in the posterior series; while in the postero- 
lateral there are often 9 in the outer and 8 or 9 in the inner row ; 
but these numbers are not always constant; both pairs of ambu- 
lacra are in slight depressions of the test. The periproct is large, oval, 
and vertical; as a rule, there are three pairs of pore-bearing plates 
between the subanal fasciole. The bare ambulacral spaces below 
