ECHINODERMATA. 61 



rocky shores. The Sand-stars ( Qphiura), the Long- 

 armed Brittle-star (Ophiocoma Jiliformis), and some 

 of the worm-like forms among the Sipunculidce, 

 resort to sandy bottoms. The Starlet (Asterina) 

 delights in those weed-fringed pools that afford 

 such a copious source of entertainment to the 

 naturalist. Several of the small species of Brittle- 

 star ( Ophiocoma neglecta, 0. Ballii, &c.) are fre- 

 quently found under stones at low water, together 

 with several kinds of the Pentactidw, and the 

 Purple-tipped Urchin (Echinus miliar is). The 

 Purple Urchin (E. lividus) excavates hollows for 

 itself in limestone rock, in which it resides ; this 

 species is confined to Ireland. The Heart-urchins 

 (Spatangidw) chiefly resort to a bottom of mud 

 or silt, in rather deep water. The Sipunculi in- 

 habit old shells of univalve MoUusca, and several 

 of the kindred kinds dwell in narrow crevices of 

 rocks. But the great majority of the species are 

 brought up by the dredge from a hard bottom ; 

 and the most prolific of all localities are those 

 banks on which oysters and scallops breed, and 

 the places frequented by trawlers, where the refuse 

 of the trawl has been thrown overboard for ages. 

 Such situations never fail to afford the richest 

 harvests to the dredger. 



Authorities. — Professor E. Forbes's " History 

 of British Starfishes" is the classic work on our 

 native species ; very few having been discovered 

 since the publication of that volume. I have 

 slightly deviated from him in the general arrange- 

 ment, in this respect following Dr. Gray's order 

 suggested in the Synopsis of the British Museum, 

 1841. 



