76 PEOr. P. M. DUNCAN ON A. 



The arm-spines are usually four in number, and the upper and 

 lower are the smaller. All are rather short, none being longer 

 than a lower arm-plate, and they are cylindro-conical, constricted 

 at the base and bulging above ifc, and thence tapering to the end. 

 They are serrate and have large terminal, and occasionally lateral, 

 glassy thorns, and they are striated longitudinally. The lowest 

 spine of the third or fourth side arm-plate has a large thorn on 

 one side, and this is larger on the spine of the next plate ; still 

 further out this lateral thorn becomes a curved hook ; and 

 at the seventh or eighth plate there is a double transparent 

 claw forming part of a hooked spine ; these hooks are large 

 and are continued to the end of the arm. 



One tentacle-scale is seen on the arm, and it is large, thin, 

 ragged and spinuled at the free edge, and it is longer than broad. 

 There are no tentacle-scales within the angles of the mouth, and 

 the first is thus absent. 



This remarkable Ophiuran came up with the sounding-apparatus 

 from off the sea-floor at a depth of 228 fathoms, about 50 miles 

 north and east of Cape Valloe, East Greenland, and about 200 

 miles from Cape Farewell, date July 19, 1860, North latitude 60° 

 42', longitude 41° 42' W. Dr. Wallich informs me that the " cup " 

 came up full of fragments of granite and felspar, to which were 

 adherent small corallines. Some of them were very delicate, and 

 their perfect condition indicated an undisturbed state of the bottom 

 water where they occurred. There was a sudden decrease of depth 

 close to the spot, and the water shallowed 578 fathoms in three 

 miles. 



Although a young form, this specimen presents the normal 

 structures of an Ophiuran, and it is in no way deformed or 

 abortive. The extreme simplicity of the oral apparatus is in itself 

 remarkable : there are true teeth, but the spines on the side mouth- 

 shields are the only mouth-papilla?, and they are so called because 

 it is the fashion, erroneously, so to call all growths from the sides 

 of the jaw-angles and side mouth-shields. The use of the small 

 spines on the side mouth-shields is that of tentacle-scales, and 

 they can have nothing to do with alimentation. This remark 

 holds good in the majority of instances where the spine arises 

 from the jaw, close to the side mouth-shield and tentacle-opening. 



There are no tooth-papilla?, and the knob-like projection within 

 the jaw-plate beneath the true teeth, so like that of some Amphiu- 

 rans, is not seen ou all the angles. It comes doubtfully, however, 

 within the description of mouth-papilla?, and appears to be a true 



