192 SPATANGACE.E. 



body presents a naked but capacious mouth, from which 

 run five almost smooth avenues, two lateral and short, 

 two backwards and extended, inclosing- the broadly ovate 

 post-oral spinous space, and one in front running to the 

 anterior groove. The five oral ambulacra are very short, 

 and resemble the dorsal one in shape. With the excep- 

 tion of the avenues the whole of the under surface is 

 studded with mammillary spiniferous tubercles, which are 

 very much larger than those on the back, as indeed are 

 the spines. The spines are hair-like and pointed on the 

 back and sides, but spathulate on the post-oral spaces. 

 Mr. Couch states in his " Cornish Fauna," that the animal 

 burrows by means of the lesser spines, and then covers 

 itself by means of the long ones on the back. From the 

 ambulacral pores on the back very long ringed worm-like 

 suckers are protruded, while from those round the mouth 

 short tentacula, with disks, surrounded by numerous clavate 

 tentacular filaments, proceed. This difference of form was 

 noticed by Muller, and is common to the tribe. 



When alive, this species is of a yellowish white colour, 

 and usually measures about an inch and three quarters 

 in length by very nearly the same breadth, and nearly one 

 inch and a quarter in height posteriorly. Young shells 

 are generally longer than broad, but old ones have a 

 tendency to become broader than long. In a gigantic 

 specimen found by the Rev. Gilbert Laing in Ireland, 

 which I owe to the kindness of my friend, Dr. Balfour, 

 the breadth exceeds the length by more than a quarter of 

 an inch. This remarkable specimen measures three inches 

 in length and two in height, and has the sub-anal im- 

 pression transversely oval, and broader than long. Saving 

 the last character, however, it presents no grounds for 

 separation as a species, though the attention of observers 



