MARINE INVERTEBRATA OF GRAND MANAN. 13 



The characters particularly mentioned in this description arc those in which 

 our species most differs from that of Greenland. Tlie arms and prominent parts 

 of the disk are bright yellow, and the depressed or membranous parts of the disk 

 dark brownish. 



This species is not uncommon at Grand Manan. It is found in the coralline 

 zone, especially among forests of Boltenim. 



OPHIURIDiE. 



Opiiiolepis tenuis, Ayres, Bost. Proc., iv. 133. Frequent among nullipores 

 below low-water mark. 



0. ROBUSTA, Ayres, Bost. Proc, iv. 134. A small graceful species, with flat disk 

 and long slender arms tapering to mere threads. It is always highly colored, 

 usually variegated with red, but sometimes jet black. It varies very much in its 

 proportions, some disks having arms doubling in length those of other disks of the 

 same diameter. It is abundant in the laminarian zone, and sometimes also at low- 

 water mark, on I'ocky and nuUipore bottoms. 



0. CILIATA, Miill. ct Trosch., Syst. der Asteriden, 91. 0. acufera, Ag., Proc. Am. 

 Acad., 1851. This species is much larger than the preceding, of a bluish-gray color 

 above, and white below. It is also very different in station, being found only on 

 muddy bottoms and in deep water. I have taken it at a depth of GO fathoms. 



Ophiophglis scolopendrica, M. et T., 1. c, 9G. Opidura muleata, Gould, Inv. 

 Mass. Excessively common in the laminarian zone, and also under stones at low 

 water. In this latter station I have found, in August, my largest specimens. 



Ophiacantua spinulosa, M. et T., 1. c, 107. A fine purplish-brown species, with 

 long rough spines on the arms, and minute crowded ones on the dorsal surface of the 

 disk. It varies considerably, and has often the aspect of an Ophiothrix. It is 

 found sparingly on shelly bottoms in the coralline zone. 



Our northern species of OphiarUIie seem yet far from being well determined. 

 One who is so fortunate as to possess very few specimens, soon becomes perfectly 

 satisfied in his own mind as to the specific distinctions, and finds little difficulty in 

 separating them ; while one who has some hundreds, can make but slow progress, 

 the perplexity seeming to increase with the number of specimens. I liave, I trust, 

 properly defined tlie limits of our New England species, by the examination of very 

 numerous individuals from many localities, in which determination I have been 

 most aided by the consideration of their habits, and especially of their association. 

 The great difficulty now remaining is their identification with those of Northern 

 Europe. So much discrepancy exists in the views of transatlantic naturalists, that 

 a very general reliance only can be placed on their figures and descriptions ; and 

 the few specimens which have yet reached this country from Scandinavia and 

 Greenland are still insufficient. So that, although I have mentioned 0. temm and 

 0. robuda under the names given them by an American author, I am yet confident 

 that they can be referred to European species when these latter shall be better 

 digested. 



