338 THE VOYAGE OF H.M.S. CHALLENGER. : 
No pedicellariz of any kind are present. 
Colour in alcohol, a yellowish or ashy grey, with a tendency to a dirty ight 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°°0 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 paxille 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 paxille, noticed in 
Mimaster cognatus, 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 cognatus. 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 cognatus, whilst it is completely hidden in Mimaster tizardi. 
A very interesting feature may here be noticed. In the abactinal skeleton of 
Mimaster cognatus the plates at the sides of the ray (¢.e., the bases of the paxille) 
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 &, Perrier, 1884. 
I have followed M. Perrier in recognising this small group of forms as an independent 
family. Although the Antheneide 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 cireumstance, 
it seems to me a better course to regard them as a distinct family than either to place 
them as a sub-family of Pentagonasteridze, or to separate the genera and apportion them 
to the families to which they have the closest superficial resemblance. 
