C42 THE VOYAGE OF H.M.S. CHALLENGER. 



crowded pedicellarise. The length of the longest is about 2 inm. ; aud their delicacy is so 

 o-reat that when denuded of the membranous sheath, they are almost invisible. to the naked 

 eye. The actinal spines do not perhaps generally stand perpendicularly, but are directed 

 laterally at a small angle to the horizontal, the plane of the direction of these spines almost 

 coinciding with that of the lateral spines, with which at first sight they might almost be 

 ranked. No inner spinelet of any kind is present on the furrow-margin of the plate. 



The actinostome occupies nearly the whole of the actinal surface of the disk, its diameter 

 being 4-5 mm., that of the disk being 6 mm. The buccal membrane is of great delicacy, and 

 perfectly transparent, the folds of the digestive cavity being clearly visible through it. 

 The mouth-j)lates are small and rather elongate, extending from the margin of the actino- 

 stome to the interbrachial arc, the united pair having a subhexagonal outline. The 

 actinostomial margin of the plates is comparatively broad and straight, with the faintest 

 prominence at the median line of juncture. Each plate bears one or sometimes two small 

 short mouth-spines, 0*36 mm. in length, on the adoral margin away from the median line, 

 directed horizontally over the actinostome, but at an angle to the median interradial line ; 

 when two mouth-spines are present the outer one is at angle of about 45°, and the inner 

 one less than this. These mouth-spines can also be directed perpendicularly. Both are 

 covered with thin opaque membrane, but bear no pedicellarise. On the actinal surface of 

 each plate, midway between the extremities, is a comparatively large secondary or super- 

 ficial mouth-spine, 1 "7 mm. in length, encased in a delicate semitransparent membranous 

 sheath crowded with pedicellarise. The sheath appears to terminate abruptly at a little 

 distance from the tip of the spine ; moreover, the pedicellarise seem to be most numerous 

 on the trumpet-shaped edge of the roll, and none are present on the basal part of the 

 sheath ; indeed, I am inclined to think that this disposition of the pedicellarise upon the 

 sheaths obtained throughout the ray. The secondary mouth-spines are twice as thick and 

 robust as any of the other spinelets on the ray. 



The plate which I regard as the madreporiform body has a very peculiar appearance, it 

 is placed quite at the margin of the abactinal surface of the disk, is subtubercular, and with 

 somewhat of a conchoidal form, having a single suture or " striation " furrow, resembling 

 the lip of certain volute shells, passing across it. The naked portion of the plate bears 

 three or four short spinelets and a few pedicellarise, the same as the other dermal struc- 

 tures of the disk, above noted. The whole structure (if this indeed be the madrepori- 

 form body) looks more like two displaced impinging plates than anything else. A distinct 

 anal aperture is present and its position is slightly excentric. 



Colour in alcohol, greyish white, with a faint pinkish shade over the ovarial regions. 



Locality.— Station 289. In the Mid-South Pacific, near the meridian of 130° W. 

 October 23, 1875. Lat. 39° 41' 0" S., long. 131° 23' 0" W. Depth 2550 fathoms. 

 Eed clay. Bottom temperature 34 Cl 8 Fahr. ; surface temperature 54°'5 Fahr. 



Remarks. — Freyella benthophila is characterised by the presence of six rays, a number 



