MUSEUM OF COMPARATIVE ZOOLOGY. 233 



Ophiothrix Orstedii Ltk. 

 Ophiothrix Orstedii, Vid. Medd. p. 15. 1856. 

 Key West, Florida, 5 specimena. 



Ophiothrix lineata Ltm. 



Ophiothrix lineata, Proc. Bost. Soc. Nat. Hist. VII. p. 201. 1859. 



Off Sand Key, 20 fathoms, 7 specimens. 



The single specimen brought by Professor Agassiz more than a quarter of a 

 century ago from Florida remained unique until hLs son again discovered the 

 species. 



Ophiomyxa flaccida Ltk. 



Ophiura flaccida Say.. Journ. Phil. Acad. V. p. 151. 1825. 

 Ophiomyxa flaccida, Addit. ad Hist. Oph. Pt. II. p. 138. 1859. 



Station 10, 37 fathoms, 8 specimens (young). Station II, 37 fathoms, 11 

 specimens. Station 45, 101 fathoms, 1 specimen. Sigsbee, off Havana, 175 

 fathoms, 6 specimens. 



Ophioscolex purpureus DiJB. & Kor. 



Ophios' .lex purjmrca, Of. Kongl. Vet. Akad. p. 235. 1844. 



Station 23, 190 fathoms, 2 specimens. 



Highly interesting as a North European species found, at no great depth, in 

 the West Indies. I could see no specific difference on comparing originals 

 from Scandinavia. 



SIGSBEIA gen. nov. 



Disk small, covered with heavy plates or scales, and passing, without line of 

 demarcation, into the stout arms, which can be rolled in a vertical plane. 

 Teeth and mouth-papillae ; no tooth-papilla3. Arms bearing the usual plates, 

 and in addition a large supplementaiy piece extending downward from the 

 upper arm-plate. Two genital openings in each interbrachial space, extending 

 to margin of disk. 



This singular genus forms a peciiliar group with Hcmieuryale, from which it 

 is distinguished by having ordinary upper arm-plates, instead of a mosaic of 

 small pieces. I have already pointed out (Ann. des Sc. Nat. 1872, p. 5) that 

 it belongs with the Ophiuridoe, and yet Von Martens was right in saying 

 that the rolling arms, passing, without line of demarcation, into the disk, sug- 

 gested the simple-armed Astrophytida). Indeed, on examining the arm-bone 

 joints, I find they offer a form approaching the double hour-glass joint of the 

 true Astrophyton, which gives them their mobility in a vertical plane, despite 

 their stiff, heavy plating. 



