2i8 Southcvji Cross. 



arm ; the arm-spines are numerous, but so small as to merge imper- 

 ceptibly into the tentacle scales. Under arm-plates small, separated 

 from one another by the side plates, which unite in the middle line. 

 Like Oj)/iioi/li//>Ii(i it has " the innermost pair of tentacle pores sha])ed 

 like slits, surrounded V)y numerous tentacle scales, and opening 

 diagonally into the mouth slits." Mouth-papillae as in Opliio(jly2-)ha 

 (0])hivra). 



It is very likely that Ophiosteira is derived from Ophiura, but 

 the keel-like plates on the tlisc, the serrated keel formed by the 

 upi^er arm -plates, and the reduction in size of the arm-spines, are 

 points by which this Antarctic form may be distinguished from any 

 Dphiurid yet known to us. 



8. OriiiosTEiKA ANTARCTICA. (PI. XXVI. aud XXVI 1.). 



AV'ith the e.\ceplion of the large plates noted in the generic 

 diaiinot^is nothing definite can be said as to the plates on the 

 upper surface of the disc, for, as Plate XXVII. .shows, the most 

 extraordinary variations are to be seen. 



The colour of the specimens in spirit is more constant ; the 

 greater part of the disc is dark grey, and the arms cream-yellow. 

 The disc is high and arched ; the arms taper gradually and carry 

 about eight very short spines ; the side arm-plates have a swollen 

 appearance. 



Diam. of disc. Lengtb of arms (ca.). 

 8 mm. 20 mm. 



7'o mm. 19 mm. 



10 mm. 26 mm. 



Stations. — Cape Adare : 26 fathoms : Nov. 4th, 5th and 10th, 

 1899 (28-8° F.). 



Cape Adare : 20 fathoms : Jan. Gth, 1900 (20° F.). 

 Cape Adare: 24 fathoms: Jan. Gth, 1900 (20" F.). 



OPHIONOTUS. 



A genus allied to Ophiura {Opliioylijpha), Init distinguished by 

 having a numljer of supernumerary arm-plates, no incision to the 

 (lisc above, and no comb of spines at the base of the arms. 



These characters in combination appear to be sufficient to justify 

 the formation of a new genus, and an opportunity such as this may 

 be taken for pointing out that an exhaustive revision of the genus 

 Ophiura would be a real service for students of brittle-stars. 



