476 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



FIG. 5. Ophiothrix expedita: 



a, club spines of the dorsal surface of the disk. 



b, spines of the dorsal surface of the disk. 



c, second arm spine. 



d, first ventral arm spine transformed into a hook. 



e, tentacle scale. 

 6. Ophiothrix foveolata: 



a, tentacle scale. 



b, second arm spine. 



c, first ventral arm spine transformed into a hook. 



d, lateral arm spines. 



PLATE 99. 

 FIG. 1. Ophiothrix galatheae: 



a, club spines of the dorsal surface of the disk. 



b, club spines of the dorsal surface of the disk in the interradii, 



in an individual from Billiton. 



c, various lateral arm spines. 



d, second lateral arm spine. 



e, third lateral arm spine. 



f, first ventral arm spine transformed into a hook at some distance 



from the disk. 



g, first ventral arm spine nearer the disk. 



h, first ventral arm spine at the beginning of the arm. 

 i, tentacle scale. 



2. Ophiothrix hirsuta: 



a, club spines of the dorsal surface of the disk. 



b, first ventral arm spine transformed into a hook. 



c, first ventral arm spine commencing to be transformed into a 



hook. 



d, tentacle scale. 



e, lateral arm spines. 



f, second arm spine. 



g, lateral arm spines toward the extremity of the arm. 



3. Ophiothrix hybrida: 



a, spines of the dorsal surface of the disk. 



b, lateral arm spines. 



c, tentacle scale. 



d, first ventral arm spine transformed into a hook. 



4. Ophiothrix koreana: 



a, club spines of the dorsal surface of the disk; normal forms. 



b, club spines of the dorsal surface of the disk; simplified forms. 



c, more or less developed spines of the dorsal surface of the 



disk. 



d, second arm spine. 



e, first ventral arm spine transformed into a hook. 



f, tentacle scale. 



PLATE 100. 



FIG. 1. Ophiothrix infirma: 



a, club spines of the dorsal surface of the disk. 



b, second arm spine. 



c, first arm spine transformed into a hook. 



d, tentacle scale. 



