340 A. E. Yerrill — North American Ophiivroidea. 



0. vepratica. One, large, conical. 

 0. segesta. One, small, acute. 



* 0. gracilis. One, slender, palmate, distal ones acute. 

 0. pectinala V. Spinif orm, two or three on first joint. 



XII. 



Tentacle-scales wanting. Adoral shield as in XIII. ( OpMopora V.) 

 0. JBartleUi (see p. 345). Outer oral tentacle-pore large, with a 

 conical papilla. 



XIII. 



Adoral shields long, usually trilobed ; the distal lobe separates 

 the oral shield from the side arm-plate. In all typical species of 

 the genus the oral shield and adoral shield both join the side arm- 

 plate. 



A. — One or two tentacle-scales. 

 B. — Disk-scales mostly concealed. 



a. — Jaws not granulated, or only slightly so. ( Ophiopristis V.) 

 b. — A row or series of special distal oral papillae. 



0. hirsuta. (See p. 336.) 

 O. ensifera. (See p. 336.) 

 0. ce7'vicorms. (See p. 347.) 



bb. — One or two distal oral papillae or scales. ( Op>hiotreta V.)f 

 O. sertata. (See p. 348.) 

 0. lineolata. (See p. 348.) 



AA. — Jaws granulated. ( Ophiolimna V.) 



* 0. Bairdii. (See p. 346.) 



0. mixta (Lym., as Ophiochmta). See p. 346. 



BB. — Disk-scales entirely exposed. Radial shields more or less 

 naked. Adoral shields broad distally. ( Ophiothamnus.) 



*0. gracilis Ver. Disk-scales bear hour-glass-shaped spinules 

 with a terminal group of points. 



AA. — No tentacle-scales. Tentacle-pores all \evy large and open. 

 ( Ophiopora V.) 



0. Bartletti. (See p. 345.) 



f Among extralimital species that belong to this gronjD, are O. placeniUjera 

 (Lym.) and O. Valencienixesi (Lym.). 



