42 University of California Publications in Zoology. [Vol.6 



Genus Ophiactis Ltk. 1856. 



Disc round and stout and covered with radial shields and 

 imbricated scales, the latter usually hearing small spines. Teeth. 

 No tooth papillae. Mouth angle short and narrow, with few (2-4) 

 small mouth papillae. Arms somewhat depressed, in length 4-7 

 times the diameter of the disc. Arm spines short and smooth. 

 Two genital openings, beginning outside th/ mouth shields. 



Ophiactis arenosa Ltk. 



Fig. 16a. Ophiactis arenosa, Ltk., partial view. 

 Fig. 16k. Partial ventral view of same. 

 Liitken, C. F. "Bidrag til Kundskab oin Nlagest.jorne, III,'' 

 Videusk. Meddel. naturhist. Foren i Kjobenh. 1856. 



Diameter of disc 6 mm. Length of arm about three and one- 

 third times diameter of disc. Disc covered with radial shields and 

 imbricated scales, the latter in interbrachial spaces and on edge of 

 disc bear each a small spine on its outer edge. Teeth. No tooth 

 papillae. One or two pairs of thin mouth papillae in each jaw. 

 Mouth shield quadrilateral, inner angle sharp, the other angles 

 rounded, outer edges convex. Side mouth shields meeting to 

 form a continuous ring round the mouth. Genital openings be- 

 ginning at mouth shield. One Hat tentacle scale. Under arm 

 plates about as broad as long. Upper arm plates broader than 

 long, narrowed proximally. Five arm spines, upper one less 

 than one arm joint, middle three each about one and one-half arm 

 joints and lower one about one arm joint in length. Color of 

 dried specimen cream with fuscous mottlings. 



West coast of Central America. San Diego Bay near National City, in 

 sponges, June, 1908, 15 specimens. 



Genus Amphiura Forbes 1842. 



Disc small and delicate, covered with overlapping scales and 

 naked radial shields. Teeth. No tooth papillae. Mouth angle 

 small and narrow with few (usually 4-6, seldom 8-10) small 

 mouth papillae. Arm long, slender, even and more or less flat- 

 tened. Arm spines short and regular. Two genital openings in 

 each interbrachial space. 



