222 ECHINODERMS OF THE BRITISH ISLES 



also the radial shields are slightly larger, ca. half the disk radius, 

 and the arm spines a little longer and more slender than in the 

 typical form. There are, however, all transitional stages, so that 

 this form can hardly be maintained as a distinct variety, still less 

 as a distinct species, as is done by several authors. 



This species is viviparous and hermaphrodite ; it is phosphor- 

 escent. It is liable to lose its disk on rough handling {e.g. in the 

 dredge). It occurs on a sandy or stony bottom, especially under 

 stones between tide-marks, also among the roots of algae, especially 

 CoralUna. A Copepod, Cancerilla tuhulata DalyeU (of the famib 

 Astrocheridae), is not rarely found as a parasite on this Ophiuroid, 

 usually attached to the ventral side of an arm, near the mouth. 

 In the bursae another, very much reduced, parasitic Copepod, 

 Philichtliys amphiurce Herouard, occurs, and, finally, the remark- 

 able Rhopalura Giardii Metschnikoff, of the family Ortho- 

 nectidse, lives in the body cavity of this Ophiuroid. 



In British seas this species is common round all the coasts. 

 It is of cosmopolitan distribution, in temperate and warm seas. 

 The bathymetrical distribution is from the tide-marks down to 

 ca. 250 m. The variety longispina would appear to belong more 

 to the deeper water than does the typical form, down to ca. 480 m. 



VII. Family Amphilepid^ ^ 



In general aspect very like the Amphiurids, but distinguished 

 by having a single, unpaired infradental papilla, and by the 

 second tube-foot being wholly outside the mouth edge. 



Only one genus in British and European seas.^ 



1. Amphilepis Ljungman. 



Disk very fiat, covered with naked scales. Mouth papillae 

 in a continuous series. No bursae ; ^ a small spot between the 

 large genital plates, covered over with thin skin, probably serves 

 for the passage of the genital products. Arms very long and 

 slender. 



Only one species known from British and European seas. 



1. Amphilepis norvegica hjungmsin. (Fig. 126.) 



Disk covered on both sides with fine scales, among which 

 the primary plates are distinct. Radial shields large, triangular, 



^ Perhaps more correctly ^^Amphilepididce^\ 



2 The genus Amphiactis Matsumoto, usually referred to this family, in 

 the opinion of the present author, belongs to the Ophiactidaj (cf. p. 198). 

 ^ It is unknown whether this holds good for all the species of this genus. 



