574 



Length 55 mm; width 21 mm; height midway between anal and 

 aperatures, about 20 mm. 



Habitat. — Monterey Bay, California, probably at a depth of 

 about 120 metres or less. 



Description. — The general form of the animal is better appre- 

 ciated from the accompanying figure than from description. Compared 

 with most species of Psolus the scales are remarkably thick , and their 

 surface is uneven, sometimes rough, but not covered with granules. The 

 upper and free edge of each scale is very prominent and stands out a 

 little distance from the next scale above, the interval being occupied by 

 small granulelike plates immersed in membrane. These small plates 

 vary from about 0,25 to 1 mm long, are usually roughly elliptical in 

 general form, and are more conspicuous between the scales of the anal 

 cone, and those of the medio-dorsal area than elsewhere. The larger 

 jjlates or scales are too irregularly arranged to form definite tiers or 

 series but they decrease in size toward the edge of the body where there 

 are 2 or 3 series of very small plates identical with those just described. 

 The anal protuberance is made up of about 5 not very regular concentric 

 series of pointed scales, the innermost series comprising 5 small tooth- 

 like scales covering the aperature. Similarly, the tentacles and neck 

 are surrounded by 2 alternating series of 5 triangular scales as shown 

 in the figure. The scales of the inner series appear to l)e rather truncate 

 with a median tooth, and the lateral parts of each scale are covered 

 with vertical rows of little plates or granules identical with those oc- 

 cupying the intersticies between the large scales of the body. The ten- 

 tacles are not fully expanded and 1 appears to have been lost. They 

 present no points of peculiarity. Around the edge of the sole the pedi- 

 cels appear to be numerous. Although the former is considerably con- 

 tracted, either lateral band of pedicels is wider than the naked space 

 between the median and lateral bands. There is 1 row of pedicels on 

 the very edge of the sole ; then about 3 mm distant another series. The 

 third series is adjacent to the second and occupies the center of the 

 band. The remainder of the pedicels are very crowded and form possibly 

 3 very irregular series, but anteriorly and posteriorly they have no serial 

 arrangement. On the midventral ambulacrum the pedicels form 2 series 

 except at either end where the band joins those of the lateral ambulacra; 

 here the middle band abruptly widens out, especially at the anterior 

 end ; much less noticeably at the posterior extremity. 



The deposits in the sole (which is thick and leathery) consist of 

 numerous, flat, subcircular, elliptical, or occasionally irregular perforated 

 plates, bearing few to many knobs on the surface. When the knobs are 

 numerous their irregular ends appear to join forming the characteristic 



