ECHINUS. 145 
Antilles, and as far north as the Faeroe Channel. From 150- 
1242 fms. 
a-e, OF S.W. coast of Ireland, 1000 fms. ‘Flying Fox’ Exp. 
Jf. Off S.W. coast of Ireland, 500 fms. Royal Dublin Soe. 
g. Three fragments, marked “ Calveria Phormo- 
soma. Types of Porcupine.” 
2. Phormosoma urauus. 
Phormosoma uranus, Wyv. Thoms. Voyage of ‘ Challenger’ (The 
Atlantic) (1877), i. p. 146, figs. 35 & 34; A. Ag. Chall. Rep. (1881) 
p- 103, pl. xvili.e. fig. 12; 7d. Mem. Mus. C. Z. x. (1883) p. 35, 
Is. x. & xi.; 7d. Proc. Roy. Soc. Ed. xi. (1883) p. 697; Rathbun, 
Proce. US. Nat. Mus. ix. (1886) p. 268; Sladen, Proc. R. Irish 
Acad, i. (1891) p. 701. 
Phormosoma petersii, A. Ag. Bull. Mus. C. Z. viii. (1880) p. 76. 
Test very thin; large primary tubercles not greatly developed till 
a late period of growth, and then “not closely packed but irregu- 
larly arranged” and limited to region near the ambitus. When 
collected of a brilliant claret colour. 
Distribution. Both sides of Atlantic from Lesser Antilles to Faeroe 
Channel. 399-1742 fms. 
A specimen dredged by H.M.S. ‘ Knight Errant’ from 555 fms., 
N.W. of Lewis, was referred to this species by Prof. Agassiz. 
ECHINID (see p. 30). 
Key to the Genera of Echinide. 
A. Three pairs of pores in an arc......... 1. Ecuinus, p. 145. 
B. More than three pairs of pores in an are. [p. 155. 
i. With moderate gill-cuts ........ 2, STRONGYLOCENTROTUS, 
li. With deep gill-cuts ............ 3. SPHARECHINUS, p. 158. 
1. ECHINUS. 
Echinus, Linn. Syst. Nat. ed. x. (1758) p. 663 (pars); Ag. wm Val. 
Anat. Echin. (1841) p. ii; Desor, Syn. Ech. foss. (1858) p.123; A. Ag. 
Rev. Ech. (1872) pp. 121, 293; Carus, Prod. Faun. Med. (1884) 
p- 100: Dune. J. Linn. Soc. xxiii. (1889) p. 126, ‘ 
Heliocidaris (pars), Desml. ef. Ag. §& Des. Ann. Set. Nat. (2) vi. 
yh D 
Spheerechinus (pars), Dj. § Hupé, Echinod, (1862) p. 529. 
Psammechinus, Ag. et Des. t. c. p. 368 (subg.) ; Desor, Syn. Ech. foss. 
(1858) p. 118; Liitken, Vid. Medd. 1863 (1864), p. 140. 
Test varies greatly in size and shape, often swollen at ambitus ; 
ambulacra rather narrow, ares of pores more or less vertical ; 
primary tubercles subequal in all parts of the test, more closely 
packed below than above the ambitus. Peristome moderate or small, 
slits slight; membrane sometimes covered by secondary calcareous 
plates in addition to the five pairs of small radial plates. Spines 
never long, acutely pointed, sometimes quite sharp. 
L 
