•48 University of California Publications in Zoology. [Vol. 6 



Family Ophiacanthidae E. Perr. 1891. 



Side arm plates well developed, usually meeting above and 

 below. Numerous long spines. Mouth papillae usually numer- 

 ous, forming a continuous row. First ventral arm plate usually 

 concave within and bearing two papillae. Generally one median 

 tooth papilla, sometimes several or a large cluster. 



Genus Ophiacantha M. T. 1842. 



Disc swollen and covered with a thin skin that obscures the 

 underlying coat of fine imbricated scales, sometimes covers the 

 radial shields and bears spines, thorns or rough grains. No tooth 

 papillae. Mouth angle large and bearing 7-16 papillae. Four 

 to eleven usually rough or thorny arm spines. Side arm plates 

 nearly or quite meeting above and below. Two genital opening's. 



Ophiacantha normani Ly. 



Figs. 18, 19. 



Bull. MuB. Comp. Zoo. Harvard, VI. No. 2, p. 58, pi. XI. 



Diameter of disc 27 mm. Length of arm about 6 times diam- 

 eter of disc. Disc covered with imbricated scales bearing small 

 sharp spines and partly covering the radial shields. One median 

 and 4 pairs of mouth papillae on each jaw and one minute pair 

 in corner of mouth. Mouth shield compressed radially, extended 

 aborally into a blunt process. Side mouth shields narrow, meet- 

 ing within. Genital pores beginning at mouth shield. One small 

 sharp tentacle scale. Ventral arm plates ellipsoidal. Side arm 

 plates meeting below. Dorsal arm plates triangular and bearing 

 minute papillae on their convex distal margins. Four slender 

 sharp ami spines, the upper one sometimes as long as three arm 

 joints, the others decreasing in length downward. Color (pre- 

 served) muddy white. 



Eastern and Western Pacific. San Diego M. B. L. : 1072, La Jolla Sta- 

 tion, 600 fathoms. 



Section 2. Polyodontida, Ludwig & Hamann, 1901. 

 Tooth papillae numerous. 



