ECHINUS. 145 



Antilles, and as far north as the Faeroe Channel. From 150- 

 12 12 fins. 



a-e. Off S.W. coast of Ireland, 1000 fms. ' Flying Fox ' Exp. 



/. Off S.W. coast of Ireland, 500 fins. Royal Dublin Soc. 



y. Three fragments, marked " Caloeria Phormo- 

 soma. Types of Porcupine." 



2. Phormosoma uranus. 



Phormosoma uranus, Wyv. Thorns. Voyage of ' Challenffer' (The 

 Atlantic) (1877), i. p. 146, figs. 33 & 34 ; A. Ay. ('hall, Rep. (188 1 ) 

 p. 103, pi. xviii. c. fig. 12; id. Mem. Mus. C. Z. x. ^1883) p. 35, 

 pis. x. & xi.; id. Proc. Roy. Soc. Ed. xi. (1883) p. 607 ; Rathbtm, 

 Proc. U.S. Nat. Mus. ix. (1880) p. 268; Sladen, Proc. R. Irish 

 Acad. i. (1891) p. 701. 



Phormosoma petersii, A. Ay. 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 Facroo 

 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. 



ECHINLD^ (seep. 30). 



Key to the Genera of Echinidae. 



A. Three pairs of pores in an arc 1. Echinus, p. 14-5. 



B. More than three pairs of pores in an arc. [p. 155. 



i. With moderate gill-cuts 2. Strong yxockntro i us, 



ii. With deep gill-cuts 3. Sph.t.reciunus, p. 158. 



1. ECHINUS. 



Echinus, Linn. Syst. Nat. ed. x. (1758) p. 663 (pars) ; Ay. in Val. 



Anat. Echin. (1841) p. ii ; Desor, Syn. Ech. foss. (1858) p. 123 ; A. Ay. 



Rev. Ech. (1872) pp. 121, 293; Cams, Prod. Faun. Med. (1884) 



p. 100; Dune. J. Linn, Soc. xxiii. (1889) p. 126. 

 Heliocidaris (pars), Desml. ef. Ay. fy Dcs. Ann. Sci. Nat. (2) vi. 



p. 371. 

 Sphperechinus (pars), Duj. §• Hupe, Eehinod, (1862) p. 529. 

 Psammechinus, Ay. et Des. t. c. p. 368 (subg.) ; Desor, Si/n. Ech. foss. 



(1858) p. 118 ; LUtken, Fid. Medd. 1863 (1864), p. 140. 



Test varies greatly in size and shape, often swollen -at ambitus ; 

 ambulacra rather narrow, arcs 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 



