336 A. E. Verrill — North American OpMuroidea. 



0. cosinica Lym., '78. Arm-plates only a little joined. 

 0. liiieolata Lym., '83. Arm-plates broadly joined. Disk with 

 grains and some spines. 



ee. — Jaws also more or less granulated. 



0. mixta (Lym., '78). Disk with grains and spines. ( Ophiolimna 

 v., p. 345.) 



eee. — Disk granulated ; radial shields partly naked. 

 f. — Radial shields joined. {Ophiacanthella V., p. 344.) 



O. Troscheli Lym., '78. 

 ff. — Radial shields separated. {Ophialcoea V., p. 331.) 



0. Nuttincjii Ver., 1899a, p. 46. 



act. — Spines partly distinctly flattened and serrulate on the edges ; 

 the rows not approximate dorsally on the basal joints. 

 Two or three tooth-papillae. ( Ophiopristis V., p. 347.) 



0. hirsuta Lym., '75. Spines four or five, slender, part flat. Disk 

 with long, very slender spines. 



0. ensifera Ver., 1899a, p. 47. Spines four, stout, mostly flat. 

 Disk with small, conical spinules. 



0. cervicornis Lym., '83. Spines five, mostly slender, acute. 



O. sertata Lym. Spines seven, translucent. Tentacle-scales two. 



III. 



Radial shields more or less exposed. 



A. — Radial shields partly or wholly in contact. 

 a. — Radial shields rather wide, angular. 



0. echinulata. Inner edges of radial shields wholly in contact. 

 (See Ophioscalus, p. 331, also p. 342.) 



aa. — Radial shields narrow and long. 



0. Troscheli. Shields naked and largely in contact. (See Ophia- 

 canthella, pp. 332, 344.) 



A A. — Radial shields separated, not large. 

 h. — Never entirely concealed. 



O. Icevi^yellis. Small, wide apart. (See Ophiomitrella, pp. 343, 352.) 



bb. — Sometimes nearly or quite concealed. 



