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



above the other, are attached at the extreme aboral end of the plate ; two similar 

 spinelets, also near together, stand near but not close to the adoral end of the plate, and 

 are likewise directed over the furrow. These inner or furrow spinelets are very delicate 

 and hair-like, less than 1 mm. in length, and have attached to them one comparatively 

 large pedicellaria, and occasionally apparently one or more at the base. Sometimes there 

 is only one small spinelet at the aboralr end of the plate. The actinal spine, which is 

 short (about 1 mm. in length), but robust at the base and sharply tapering, is articulated 

 on a small tubercle near the middle of the actinal surface of the plate, and is encased 

 in a delicate membranous sheath with numerous pedicellarise. The lateral spines are 

 17 to 18 mm. in length at 100 mm. from the base, very delicate, slender, and tapering, 

 and are covered with an exceedingly thin membrane crowded with minute pedicellarise 

 and presenting a considerable saccular prolongation at the extremity. Each lateral spine 

 is articulated on a small subtriangular plate — the rudimentary representative of an infero- 

 marginal plate — attached by suture to the lateral margin of the adambulacral plate, and 

 with its adoral side rounded, the last-named feature causing the plate at first sight to 

 appear as a truncate tubercular eminence on the adambulacral plate. At the extreme base 

 of the ray there are two of the rudimentary infero-marginal plates : the first, which arti- 

 culates on the odontophore, is as long as the underlying adambulacral plate, but diminishes 

 rapidly in height between its adoral and aboral ends ; the second margiual plate is shorter 

 than the first and tapers to a point. Beyond this are several elongate scale-like plates, 

 which may perhaps be an aborted continuation of the marginal plates. 



Locality.— Station 160. South of Australia. March 13, 1874. Lat. 42° 42' 0" S 

 long. 134° 10' 0" E. Depth 2600 fathoms. Red clay. Bottom temperature 33°9 Fahr. ; 

 surface temperature 55 o- Fahr. 



Remarks. — Brisinga discincta is characterised by the almost complete abortion of the 

 abactinal skeleton, this being represented only by a few minute plates on the ovarial region, 

 which do not form a single entire transverse band. So far as I can judge from the frag- 

 ments collected the alliance of this species to the form described by Perrier under the 

 name of Hymenodiscus appears to be very close, and lends support to the doubt which I 

 have expressed as to the generic independence of that form. Brisinga discincta may be 

 further distinguished from the other members of the genus by the absence of tegumentary 

 prickles in the abactinal membrane, by the presence of three or four inner spinelets in the 

 armature of the adambulacral plates, and by the length of the lateral spines. 



Genus Freyella, Perrier. 



Freyella, Perrier, Ann. Sci. Nat. (Zool), 1885, t. xix. Art. No. 8, p. 5. 



The genus Freyella, like the genus Odinia, is due to the critical insight of M. Perrier. 

 Species of both genera have previously been ranked as Brisinga, notwithstanding the 



