ECH1N0DERMATA 



95 



arms may be coiled up or folded toward the mouth, giving the 

 animal a sort of basketlike appearance (Fig. 86). The skele- 

 tal system is much less developed here, and instead the integu- 

 ment is thick ; spines are absent. 



The development of the Ophiuroidea may be direct, as in 

 those cases where the bursa? function as brood pouches, or 



Fig. 85. Ophioglypha bullata, a serpent-star, aboral aspect; enlarged about two and a 

 half diameters. (From Shipley and MacBride's Zoology.) 



there may be a bilaterally symmetrical, free-swimming larva, 

 resembling those found in other groups of the Echinodermata. 

 A few of the representatives of this class live near the shore. 

 but we find them at all depths, even in the deep sea ; some live 

 at certain depths only, others exist over a much greater area. 

 A specimen which is thirty centimeters in diameter is considered 



