SPHAERECHINUS PULCHERRIMUS. 



453 



sometimes in straight oblique lines of four pairs, or in re-entering arcs of 

 from five to six pairs of pores, according to size of specimens. Actinostome 

 small, actinal cuts deep. In the ambulacra! zone the tubercles are slightly 

 smaller than in the interambulacral region, forming from two to four regular 

 vertical rows, with an irregular median vertical line, and minute secondary 

 tubercles contained between adjoining arcs of pores along the whole poriferous 

 zone. Small miliaries are arranged in connected rings round the scrobicular 

 circles of the main tubercles, and also fill the space between the primary 

 tubercles. In the interambulacral zone the vertical rows of closely packed 

 primary tubercles are at the same time arranged in regular horizontal rows, 

 separated by vertical and horizontal lines of miliaries and secondaries forming 

 irregular rectangles. There are from two to twelve vertical rows of primaries, 

 according to size of specimens, with an irregular median line. The spines are 

 are short, stout, and, owing to the narrowness of the coronal plates, closely 

 crowded together. They are frequently of uniform color, either violet-brown, 

 yellowish, or tipped with white at the summit, with darker-colored shafts, or 

 wholly white. The plates covering the actinal membrane are very large and 

 prominent, arranged in the continuation of the ambulacra. Auricles are slen- 

 der, with large auricular opening and low solid connecting ridges. 



Mediterranean ; Canary Islands. 



Sphaerechinus pulcherrimus 



! Psammechinus pulcherrimus Barn.. 18G3, in A. Agass. Proe. Pkila. Ac. N. S. 

 ! Sphaerechinus pulcherrimus A. Ag., 1872, Rev. Ech. Pt. I., p. 160. 



PI. VI. f. 19. 



Test flattened, of medium thickness. Poriferous zone broader than median 

 ambulacral region, containing oblique arcs of pores arranged in four pairs, 

 separated by an oblique row of three small tubercles, with smaller miliaries 



