Ambulacral petals symmetrical, very prominent, reaching to the margin, longitudinally grooved by a median line. The outer pores of the petals abruptly depressed on each side. Inferior surface slightly concave. Mouth central, small, rounded. Ambulacral furrows straight, well marked. Anus small, sub-marginal. Papillary tubercles numerous, especially in the ambulacral areas, and in the center beneath, not prominent, situated in comparatively deep and sub-angular cavities. Greatest diameter 1.34 inches. Shortest diameter 1.26 ” Height 0.34 ” Locality: Kirker’s Pass formations; occurs as the preceding species; also two miles west of Walnut Creek House. From the collections of the California Academy of Natural Sciences, of the State Geological Survey, and my own. ECHINARACHNIUS van Phels. _E. Brewerianus_ Rém. Disk small, oval-elongated, broader behind, rather thin. Upper surface slightly convex; margin rounded. Apex posteriorly sub-central. Petals close, nearly symmetrical, the anterior and posterior ones the longest, as wide as or even wider than the inter-ambulacral spaces; ambulacral areas composed of very narrow plates, widening on the margin. Inferior surface plane. Ambulacral furrows not visible in the specimens examined. Mouth small, central. Anus very small, sub-marginal. Papillary tubercles numerous, rounded, somewhat prominent, more crowded beneath than above. Length 1.22 inches. Width 1.06 ” Height 0.30 ” Locality: Two miles east of Walnut Creek House; from miocene beds. Collection of the State Geological Survey, and mine. This species is dedicated to Prof. W. H. Brewer, Botanist to the Survey. CLYPEASTER Lamark. _C. Gabbii_ Rém. Disk rather small, comparatively thick, varying from circular to sub-pentagonal and irregular sub-oval. Apex nearly central, sub-elevated; margin rounded; genital apparatus sub-angular. Ambulacral star almost symmetrical; petals about equal in length, elongated, open at their extremities. Inferior surface flat near the edge, and gently concave in the center. Mouth depressed, sub-central. Ambulacral furrows straight, slightly marked. Anal aperture very small, marginal. Tubercles of the upper surface numerous, especially in the ambulacra, round and prominent. Greatest diameter 1.16 inches. Smallest diameter 1.10 ” Height 0.28 ” Locality: The C. Gabbii occurs abundantly on the eastern shore of San Pablo Bay, south of Mare Island, in soft sand-stones of miocene age. Collections of the State Geological Survey, and Academy of Natural Sciences; also Mr. Gabb’s, Mr. F. L. A. Pioche’s, and mine. Dr. Kellogg read the following paper: