168 



surrounded by plates more or less completely imbedded and hidden 

 in the skin. 



This genus differs from Psolus Oken in the presence of pedicels 

 on the dorsal surface; from Psolidnwi Ludwig, in the shape of the 

 body and in the fact that the pedicels are not confined to the ambu- 

 lacra on any part of the dorsal surface; and from Thêelia Ludwig in the 

 number of tentacles, the absence of plates on the back and the fact 

 that the dorsal appendages are apparently true pedicels. 



Thyo7iepsolus nutriens nov. sp. (Fig. 6 — 14). On rocks along shore 

 of Monterey Bay. 



Color in life, "red"; in alcohol yellowish-Avhite. Length 15 mm, 

 breadth 8 mm, height 5 mm. Body depressed, ventral surface (Fig. 6) 

 perfectly flat, dorsal surface 'Fig. 7) flattened. Ventral surface with a 

 thin stiff skin; dorsal surface with a very thick body wall, the inner 



Fi?. 6. Fiff. 7. 



FÌ2. 8. 



layer of which is thin and stiff, while the outer layer is thick and soft. 

 Pedicels numerous, scattered irregularly all over the dorsal surface but 

 arranged in 3 longitudinal series on the ventral side; the lateral series 

 have 4 or 5 rows of pedicels , the median only 2 (Fig. 8). Tentacles 

 apparently 8, but probably 10, seemingly of equal size. Calcareous 

 ring moderate, without posterior prolongations. Anus surrounded by 

 a number of small calcareous plates but these are largely concealed by 

 the soft outer layer of skin. Calcareous particles of the body wall, very 

 numerous. In the ventral skin, they consist of small perforated plates 

 (Fig. 9). In the body wall of the dorsal side there are 3 distinct layers: 



1) an inner layer of large fenestrated, knobbed ellipses or thick plates, 

 more or less flattened (Fig. 10); these make up the stiff part of the 

 dorsal skin and are often perforated for the passage of the pedicels, 



2) a middle layer of large and small irregular plates more or less 

 curved, perforated by many smooth holes which are largest near the 



