174 THE DEPTHS OF THE SEA. [cHAP. Iv. 
perisom. The plates of the disk are soldered 
together, so as to form a close mosaic (vceiov). 
The mouth-papille are fused into two lines, their 
number being only indicated by grooves. The 
lateral arm-plates are united together above and 
below, the upper and lower arm-plates are reduced 
to mere rudiments, and there are no tentacle pores 
beyond the first arm-joints. 
Fa. 34.—Dorynchus thonsoni, NORMAN. Once and a half the natural size ; everywhere in 
deep water, 
In our new species, which I name provisionally 
Ophiomusium lymani, the diameter of the disk is 
28 mm., and the length of each arm 100 mm. in 
large specimens. The two lateral arm-plates, fused 
together above and below, form complete rings, their 
distal edge notched on each side for the insertion of 
seven arm spines, of which the lowest is much longer 
than the rest. The dorsal arm-plates are small and 
diamond-shaped, let in between the lateral arm- 
plates at the distal end of their upper line of 
