ECHINUS. 489 



ECHINUS. 



Echinus Rondel, 1554, De Piscib. (Lixx). (emend.) 

 (See Part II. p. 293.) 



Echinus acutus 



! Echinus acutus Lamk., 181G, An. s. Vert. 



PI. VII". f. 5; PI XXV. f. 12-16. 



The variation in the shape of the different species of Echinus is so great 

 that any attempt to describe the general form and outline would be useless, 

 and I shall confine myself to such special marks as are characteristic, and 

 make the description as far as possible comparative. In E. acutus the 

 general outline is slightly conical, and when seen from above somewhat 

 pentagonal, the median interambulacral space being somewhat concave ; 

 with two principal vertical rows of primary tubercles, one for each plate ; the 

 rest of the plate sparsely covered by secondary tubercles, forming an irregu- 

 lar arc above the primary. Nearer the actinostome there are two other 

 vertical rows, but they do not extend much beyond the equator on each 

 side of the primary towards the abactinal pole. Coronal plates high. 

 Median interambulacral as well as ambulacral space bare. In the am- 

 bulacral space two principal vertical rows of primary tubercles near the 

 poriferous zone, with two additional irregular ones extending from the 

 equator towards the actinostome. Auricles broad. Anal system moderate. 

 Genital plates pointed, carrying generally three small secondary tubercles near 

 the anal edge ; genital opening near the exterior edge of the plate ; ocular 

 plates pentagonal, openings distinct. Primary spines stout, tapering, usually 

 of a darker color than the test, brilliant carmine at base, tapering to white or 

 greenish tips, finely striated. This is known to Italian zoologists as E. sardicus. 



Norway ; Mediterranean. 



Echinus angulosus 



! Cidaris angulosa Leske, 1 778, Kl. Add. 



! Echinus angulosus, A. Ag., 1872, Rev. Ech., Pt. I. p. 122. 



PI. VW.f. 3. 



The longer, more slender spines, — generally tipped with violet, the shafts 

 of all shades between that and the lightest yellow, — the thinner test, the 



