ECHINODERMATA 67 



and should properly have placed the two that follow at the 

 commencement of the series. 



On sandy bottom, and on muddy ground, from low-tide 

 margin to deep water, are found in number the " Sand 

 Stars." These differ considerably from any of those 

 described. They are firm and fossil-like, having an 

 appearance as if carved out of chalk. They are Ophiura 



Fig. 26. Ophiura albida. Upper and under sides. Natural size 



albida and Ophiura texturata (Ophiura : " snake tail "). 

 The former measures about three inches across the rays, 

 the central disc being about half-an-inch across. The 

 latter, which closely resembles it, except in the arrange- 

 ment of the calcareous plates and spines, is about double 

 the size. Their colour is chalky white, with crossbanding 

 on the rays of ash-grey (Fig. 26). 



The CrinMea. This division, which is formed for the 

 reception of forms which in some respects have affinities 



