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



other hand the individual points of difference between the Chilian and the Northern 

 forms are small and trifling, but when taken as a whole may be regarded as sufficient to 

 differentiate them specificalfv, especially when the constancy of the characters in question 

 and the widely separated geographical position of the two forms are taken into account. 



Colour in alcohol, a bleached yellowish white. 



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 306. In the Messier Channel, between Wellington Island and the west coast 

 of Chili. January 2, 1876. Lat. 48° 17' 0" S., long. 74° 33' 0" W. Depth 565 fathoms. 

 Blue mud. Surface temperature 57°"0 Fahr. 



Station 307. Between Wellington Island and the west coast of Chili, off Port 

 Grappler. January 4, 1876. Lat. 49° 24' 30" S., long. 74° 23' 30" W. Depth 140 

 fathoms. Blue mud. Surface temperature 53°"0 Fahr. 



Station 309. Off Puerto Buono. January 8, 1876. Lat. 50° 56' 0" S., long. 74° 

 15' 0" W. Depth 40 fathoms. Blue mud. Bottom temperature 47°"0 Fahr. ; surface 

 temperature 50° "5 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. 



Family AsteopectiniDjE (Gray, 1840), emend. 



Several of the forms included in this family have previously been ranked in the genus 

 Ar chaster, as shown in the list of species erroneously referred to that type, given on 

 p. 122. This circumstance may be attributed in a large measure to the great similarity in 

 general fades that exists between many of the Asterids belonging to the two families 

 Archasteridae and Astropectinidse, as well as to the want of an exact limitation of the 

 generic scope of Archaster. 



On the basis of the structural characters indicated in these pages, I consider that the 

 Astropectinidse are a well-defined family, and that the genera which I have now classed 

 together constitute a natural group distinguished by special morphological features. 



Luidia, on account of its structural peculiarities, is in my opinion a very divergent 

 member of the family. The relationship of this genus is in many respects so isolated 

 that I have placed it in a distinct subfamily, in recognition of this fact ; and I have 

 associated with it, on structural grounds, the remarkable genus Platasterias of Gray, 

 which has latterly been merged in the genus Astropecten. 



The genus IJyaster of Danielssen and Koren appears to me to belong to this family ; 

 and its affinities are probably near to Phoxastcr. 



