ECHlIfOCARDIUM. 169 



1. Echinocardium cordatum. (Plate XVI. figs. 1-4.) 



Echinus cordatus, Penn. Brit. Zool. iv. (1777) p. 58, pi. xxxiv. fig. 75 ; 



id. op. cit. iv. (1812) p. 189, pi. xxxvi. fig. 2. 

 Spatangus arcuarius, Lartik. An. $. Vert. iii. (1816) p. 32. 

 Echinocardium pusillus, Gray, Ami. Phil. xxvi. (1825) p. 430. 

 Spatangus cordatus, Flem. Brit. An. (1828) p. 480. 

 Spatangus ovalis, van den Ende, Nat. Verh. Hollandsche Maatsch. xvi. 



2. (1828) p. 301. 



Ampliidotus cordatus, Forbes, Brit. Star/. (1841) p. 190 ; Thompson, 



Nat. Hist. Irel. iv. (1850) p. 442. 

 Amphidetus cordatus, Diib. # Eor. Vet. -Ah. Hdlg. 1844 (184U), 



p. 285 ; Ag. # Des. Ann. Sci. Nat. viii. (1847) p. 11, & vi. (1846) 



pi. xyi. fig. 8 ; Sars, Norg. Ech. (1861) p. 97. 

 Echinocardium cordatus, Gray, Brit. Bad. (1848) p. 6. 

 Amphidotus arcuarius, Maitland, Faun. Belg. septent. (1851) p. 91. 

 Echinocardium cordatum, id. Cat. Ech. (1855) p. 48; Duj. fy Hup. 



Echin. (1862) p. 602 ; Al. Ag. Bev. Ech. (1872) pp. 109 & 349, 



pi. xix. figs. 10-17 & pi. xx. tigs. 5-7 ; Mob. § Biits. JB. Comm. 



Kiel, ii. & iii. (1875) p. 150 ; Ludwig, Mitth. zool. Stat. Neap. i. 



(1879) p. 561 ; Koehler, Ann. Mm. Marseille, i. 8. (1885) p. 130 ; 



Carus, Prod. Faun. Mediter. (1884) p. 102 ; Fleisehmann, Zeit.f. 



tviss. Zool. (1888) p. 131 (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 arc three pairs of pore-bearing plates 

 between the subanal fasciole. The bare ambulacral spaces below 



