575 



fenestrated plates (figs. 2, 5). The edges of the plates are more or less 

 deeply scalloped or incised, the projections frequently assuming the form 

 of teeth. A slight ridge proceeds inward from each tooth for a short 

 distance so that the periphery of the plate appears to be of uneven 

 thickness, the thinner portion, of course, being opposite each incision. 

 The commoner forms of plates are shown in figures 2 to 7. These have 

 the longest diameter ranging from 0,1 to 0,3 mm, the greater number 

 being about 0,2 mm. In the pedicels near the terminal plate, which has 

 a diameter of 0,95 mm, are elongated, perforated, very slightly knobbed 



âi^^!^^ 



Fig. 1. Psolus californicus from side x 1. Figs. 2 — 7, deposits from sole x 100. 

 Figs. 8, 10, 11, 12, deposits from tentacles, x 100. Figs. 9, 13, deposits from mem- 

 brane at base of tentacles, x 100. 



plates. These pass insensibly into the ordinary circular or subelliptical 

 knobbed plates of the general perisome. In fact the elongated plates 

 are only slightly different from the elliptical ones being more irregular 

 in outline with more prominent marginal teeth. The tentacles abound 

 in small perforated plates (figs. 8 and 10), and larger perforated rods 

 and rod-like plates (figs. 11 and 12). There are also many small and 

 large more or less branched rods (fig. 9). The perforated plates are usu- 

 ally slightly curved and vary from about 0,08 to 0,3 mm, longest de- 



