PLATE CXXI. 



Fig. 

 1. Dorsal surface of the anterior region of Dasychone argus, Sars, with the branchise 



of one side, a, tentacles ; b, pigment-speck at first bristle-tuft. 

 1 a. Lateral view of a somewhat short Zetlandic example from Burra Voe. Enlarged. 

 1 b. Ova of the foregoing, x 350. 



1 c. Cephalic plate, a, oral region ; b, chordoid supporting tissue ; c, central mass ; 



d, dorsal furrow; e, dorsal incurvation. Slightly enlarged. 

 ~'~2T Cephalic plate of Ghone Fauveli, Mcintosh. Slightly enlarged. 



2 b. Ovum, x 200. 



2 c. Membranous portion of tube, x 200. 



3. Lateral view of Ghone Reayi, Mcintosh, with portion of tube. Between tide-marks, 



St. Peter Port, Guernsey. Enlarged. 



3 a. Ventral view. Enlarged. 



4. Body of Myxicola viridis, Milne-Edwards, as a transparent object, from St. Andrews 



Bay. X 60. 



5. Extremity of a branchia of Protula tabidaria, Montagu. Enlarged. 



6. Spiked opercular disc of Hydroides norvegica, Gunner. Enlarged. 



6 a. Lateral view of the anterior region of the same species. Enlarged. 



6 b. Oblique view of the opercular region. Enlarged. 



6 c. Free edge of the grooved region of the operculum. X 200. 



6 d. Tubes of the same on Gyjprina islandica, St. Andrews Bay. Natural size. 



7. Lateral view of the operculum of Serpulavermicidaris, L. Enlarged. 



7 a. Tip of branchia. X 60. 



8. Dried tubes of Filograna implexa, Berkeley, St. Andrews. About natural size. 



9. Ventral view of Ghone infund ibuliformis , Kroyer, from the "Valorous" Expedition 

 to the Arctic Sea, 1875. Enlarged. 



