66 PROCEEDINGS OF THE ACADEMY OF [Feb.,. 



Subfamily 2. HEMIEURYALINiE nov. 



(Characters as given in key, p. 65.) 

 • This subfamily includes Sigsheia, Ophioplus"^ and Hemieuryale. 



Order iii. GNATHOPHIURIDA nov. 



Radial shield and genital plate articulate by means of a con- 

 spicuous socket in the former and of a large, ball-like condyle on the 

 latter. Genital plates, as a rule, firmly fixed to the basal vertebrae. 

 Genital scales short, very wide, flattened, leaf-like. On abradial 

 side of innermost part of each genital slit occurs another short, wide, 

 flattened, leaf-like scale, which is firmly attached to oral shield. 

 Peristomal plates small, or rarely large, usually entire, but sometimes 

 double. Oral frames, as a rule, with well-developed lateral wings. 



Key to families of Gnathophiurida. 



A — Teeth triangular, with pointed ends, not very stout; oral papillae 

 present; dental papillae wanting; peristomal plates large, 

 entire; oral frames without well-developed lateral wings; 

 genital scales, short, leaf -like; genital plates free, not fixed 

 to basal vertebrae; distal vertebrae often incompletely divided 



longitudinally by a series of pores Amphilepidid^. 



AA- — Teeth quadrangular, with wide ends, very stout; peristomal 

 plates small; oral frames very stout with well-developed 

 lateral wings; genital plates firmly fixed to basal vertebrae. 

 a — Oral papillae present; no vertical clump of dental papillae; 

 dorsal side of vertebrae rhomboidal, not U-shaped, 



Amphiurid^. 

 aa — Oral papillae absent; dental papillae well developed, forming 

 a vertical clump at apex of each jaw; dorsal side of ver- 

 tebrae U-shaped Ophiotrichid^. 



Family 1. AMPHILEPIDIDiE nov. 



(Characters as given above in key.) 



This family includes Amphilepis and Ophiochytra, besides a new 

 genus, Amphiactis. Though almost similar to the next in external 

 features, this family suggests the Ophiacanthidae in many internal 

 structures. 



Amphiactis gen. nov. 



Disk covered with imbricating scales, besides moderately large 

 radial shields. Four or five oral papillae on either side of each jaw, 

 unequal in size, arranged almost in a continuous series. Teeth 



2 Ophioplus armatus Koehler, 1907, evidently does not belong to the present 

 subfamily, being, in my opinion, referable to Ophiolebes. 



