310 



ECHINODERMS OF THE BRITISH ISLES 



Tridentate pedicellariae with rather broad, leaf -shaped valves 

 (Fig. 179, 2). Colour of the spines usually violet, with the point 

 white ; test purplish-violet. Grows to a considerable size, ca. 

 130 mm. horizontal diameter. 



Breeding season in the summer-time or (in the Mediterranean), 

 throughout most of the year. The larva in the I. stage has a 

 short, rounded body, the body-rods not prolonged, but united 

 by a transverse rod with the recurrent rods, so as to form 



Fig. 178. — Sphcerechinus granularis , 

 and a naked test ; side view. 

 Echinod., Faune de France.) 



specimen with the spines preserved, 

 SHghtly reduced. (After Koehler, 



a basket structure. This young larva is very much like the young 

 larva of Echinocyamus x>usillus, and is hardly distinguishable 

 with certainty from the latter (cf. Fig. 183, 1) ; as soon as the 

 postero-dorsal rods have appeared, they are easily distinguishable, 

 the Echinocyamus larva having both postoral and postero-dorsal 

 rods fenestrated, while in the Sphcerechinus larva only the 

 postoral rod is fenestrated. In the II. stage the larva has a 

 posterior transverse rod, simply bifurcating at the ends, the lower 

 branch not developed into a long postero-lateral rod such as is 



