Fig. 8. Longitudinal section through the gill region. G., gills. B., blood. O., ovary. N., nervous network. x40. Fig. 9. Cross section of alimentary canal. A., wall of alimentary canal. x40. Fig. 10. Intestinal epithelium, modified ciliated columnar. x400. Fig. 11. Epithelium of the gill, modified ciliated columnar. x400. Fig. 12. Nervous tissue. x400. Fig. 13. Surface epithelium of proboscis, modified ciliated columnar. x400. Fig. 14. Surface epithelium of collar, modified ciliated columnar. x400. Fig. 15. Surface epithelium of trunk, modified ciliated columnar. x400. Fig. 16. Cells of testis. x400. Fig. 17. Ovary. x400. Fig. 18. Plain muscle. x400. Fig. 19. Epithelium of diverticulum. x400. Fig. 20. Connective tissue of proboscis. x400. Fig. 21. Muscle bands in proboscis connective tissue. x400. [Illustration] [Illustration] [Illustration] Opisthobranchs from Laguna Beach The determinations are by Dr. F. M. MacFarland TECTIBRANCHS _Pleurobranchaea californica_ MacF. Only one specimen has been obtained at Laguna Beach, from a depth of from 15 to 20 fathoms. The specimen was mottled dark above and about 5 inches long. Dr. MacFarland informs me that this species is quite common in Monterey Bay and ranges much larger, almost up to 10 inches in length. _Navanax inermis_ Cooper. Black, yellow lines, blue spots, yellow edges. About two inches in length. Another specimen possibly may be the same species, black with yellow spots. Apparently the same form occurs at Balboa. _Aglaja (Doridium) purpureum_ Berg.? Brown, dredged 10 to 15 f. NUDIBRANCHS _Triopha sp._ Large, brown. Holdfast. _Flabellina iodinea_ Cooper. Narrow blue body, red appendages. Swims by lateral movements of the body. This beautiful nudibranch was first found near Laguna by Miss M. Cate, not far from Dana's point in 1916. In Jan. 15, '18, Mrs. May found a number near Laguna Beach. _Dirona picta_ MacF. Light brown, long thick appendages. Holdfasts and tidepools common in 1915. _Aegires_ sp. Knobs. Brick red, body clear. _Chromodoris universitatis_ Cock. Blue, yellow spots. _Polycera atra_ MacF. Red-brown, black stripes, brown spots. July 10, 1915. _Facelina_ sp. Body clear, appendages dark. _Ancula pacifica_ MacF.? Clear white, two yellow lines in front, one behind. Front appendages and two lateral tipped with yellow. _Cadlina_ Sp.? Dark brown, flattened. _Aeolidia_ sp. White to pink, appendages brown. W. A. H. Central Nervous System of the Sand Dollar Dendraster Excentricus Esh WILLIAM A. HILTON