80 URASTERT.E. 



long ; the diameter of the disk in one direction three and 

 a half, and in another three inches : the rajs at their 

 origins were two inches wide, the breadth of the disk being 

 to the length of the ray as two and a half to twelve. The 

 specimen from which my figure was taken is of more 

 ordinary dimensions, being fifteen inches across, the longest 

 ray seven inches and a half long and one inch in breadth, 

 which was also the breadth of the disk. This species 

 varies greatly in its proportions ; but the rays are always 

 more taper in proportion to the disk than those of any 

 other British Uraster. The rays are acutely pentangular 

 and tapering, the uppermost angle forming a keel. The 

 angles are crowned by strong conic spines placed on tuber- 

 cles, and surrounded towards the base by a circle of nu- 

 merous spinules. The intermediate spaces are strongly 

 reticulated. Here and there among the reticulations are 

 scattered a few large spines similar to those on the angles. 

 The surface is also covered by little divided pincer-like 

 spinules, which organs are seen on all the species of the 

 genus. The madreporiform tubercle is small, finely striate, 

 and placed very lateral. Beneath, the avenues taper to 

 the ends of the rays, and the border spines are shorter, 

 finer, and less conic than those crowning the angles. The 

 disk is very prominent and round ; it is reticulated, and 

 provided with spines similar to those on the rays, but not 

 so numerous. The rays are not so firmly attached to the 

 disk as in the other species of Uraster. " The weight of 

 the body," 11 says Mr. Couch, " cannot be sustained, or even 

 turned over, by lifting it by the rays without separating 

 them. 1 ' I have dredged up living rays without bodies, 

 evidently in consequence of this facility of separation. It 

 is doubtful, however, whether the animal has the power 

 of throwing them off voluntarily, as is the case with Luidia 



