338 THE VOYAGE OF H.M.S. CHALLENGER. 



No pedicellariae of any kind are present. 



Colour in alcohol, a yellowish or ashy grey, with a tendency to a dirty light brown 

 shade. 



Localities. — Station 303. Off the western coast of South America, off the Chonos 

 Archipelago. December 30, 1875. Lat. 45° 31' 0" S., long. 78° 9' 0" W. Depth 

 1325 fathoms. Blue mud. Bottom temperature 36 o, Fahr. ; surface temperature 

 54° -8 Fahr. 



Station 311. Off the entrance to Smyth Channel. January 11, 1876. Lat. 

 52° 45' 30" S., long. 73° 46' 0" W. Depth 245 fathoms. Blue mud. Bottom 

 temperature 46°'0 Fahr. ; surface temperature 50° '0 Fahr. 



Remarks. — This species bears a very close resemblance to Mimaster tizardi of the 

 North Atlantic, but is readily distinguished by a number of points. The rays are more 

 elongate and distinctly narrower at the base, and are fuller and more swollen abactinally, 

 which gives them a distinctly subcylindrical appearance. The paxillse are of a more 

 radiating and stellate character, instead of compact, as in Mimaster tizardi; and the 

 difference in size between the regularly and irregularly disposed paxillse, noticed in 

 Mimaster eognatus, is not discernible in the Atlantic form. The great diminution in 

 the size of the supero-marginal plates and the increase in that of the infero-marginal 

 plates, and their consequent general character and posture, constitute a remarkable 

 difference in Mimaster eognatus. The armature of the adambulacral plates is simpler, 

 and the actinal interradial areas are less extensive. The madreporiform body is large and 

 exposed in Mimaster eognatus, whilst it is completely hidden in Mimaster tizardi. 



A very interesting feature may here be noticed. In the abactinal skeleton of 

 Mimaster eognatus the plates at the sides of the ray (i.e., the bases of the paxillae) 

 are cruciform, with four prolongations, nearly at right angles ; whilst those of the inter- 

 mediate median space of the ray are stellate, usually with five points. In Mimaster 

 tizardi, on the other hand, all are stellate or substellate, and those in the median area of 

 the rays are less definitely stellate than the lateral ones, the difference being well marked. 



Family Antheneid^e, Perrier, 1884. 



I have followed M. Perrier in recognising this small group of forms as an independent 

 family. Although the Antheneidse stand clearly apart, the characters upon which their 

 claim to family rank is based are, perhaps, somewhat artificial, or in other words, are less 

 well defined than is the case in the allied families. Notwithstanding this circumstance, 

 it seems to me a better course to regard them as a distinct family than either to place 

 them as a sub-family of Pentagonasteridas, or to separate the genera and apportion them 

 to the families to which they have the closest superficial resemblance. 



