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Abundant siliceous sponge spicules were found in the lower and middle Eocene sediments of Site 605 and the upper Miocene sediments of Site 604. The assemblages consist mostly of monaxons. Relative abundances of the various types are tabulated. All those from the Miocene sample, and the vast majority of those from the Eocene sample, belong to the Class Demospongea. A small minority of the Eocene spicules are from the Class Hexactinellida. INTRODUCTION A diverse assemblage of siliceous sponge spicules was found at DSDP Sites 604 and 605 of Leg 93 off the Atlantic coast of the United States while parts of these sections were being examined for silicoflagellates (McCartney and Wise, this volume) (Fig. 1). Siliceous sponge spicules are sometimes quite abundant in DSDP samples but are seldom discussed; among papers that do so are Dumitricà (1973), Bukry (1978, 1979, 1980a, b), and Ivanik (1983). In this study, the spicules are particularly abundant and diverse in an early and middle Eocene interval of Site 605, where they are one of the most important components of the siliceous sediment. Sponge spicules are less abundant and diverse in a late Miocene interval from Site 604. At both sites the assemblages are dominated by monaxons, with other types representing only a minor fraction of the total abundance. The vast majority of the spicules are from the Class Demospongea, including all from Site 604. Only the amphidiscs and hexactines (and the possible hexasters) from Site 605 belong to the Class Hexactinellida. METHODS Raw samples were placed in 100 ml beakers and a small amount of 30% hydrogen peroxide added; more was added if it strongly effervesced. After 2-4 hr. (or longer if effervescence continued when more hydrogen peroxide was added), the beaker was placed in an ultrasonic cleaner and distilled water was added to about the 25 ml level. HC1 was added and the beaker heated for 30 min. Samples were then centrifuged and decanted twice and washed once more before making strewn slides. Relative abundance was determined by examining an entire 22 × 40 mm slide and is reported according to the following scale (Tables 1 and 2): Dominant (D), >50% of all spicules; Abundant (A), 10-50%; Common (C), 1-10%; Uncommon (U), 0.1-1% (2-5 per slide); Rare (R), < 0 . 1 % (1 per slide). TERMINOLOGY Although Ehrenberg (1854) erected a Linnean taxonomy for fossil sponges, a descriptive terminology for isolated spicules is generally used (see Hyman, 1940; Sol1 van Hinte, J. E., Wise, S. W., Jr., et al., Init. Repts. DSDP, 93: Washington (U.S. Govt. Printing Office). 2 Address: Department of Geology, Florida State University, Tallahassee, FL 32306-3026. las, 1906; and Bukry, 1978). A usable formal spicule taxonomy is not practical because a single living species may contain a variety of spicule types, and similar spicules can be produced by different species of sponge. Ivanik (1983), however, demonstrates that sponge spicules do have some biostratigraphic and paleoecologic use. The descriptive terms used in this study to tabulate the relative abundances are listed here, with comments where applicable. Class DEMOSPONGEA Sollas Monaxons Diactinal (monaxons with similar ends) Oxeas (pointed ends; Plate 2, Figs. 1, 9): Very abundant, generally making up 30-40% of the sponge spicules at Site 605, and 60-70% at Site 604. Length and relative thickness vary widely and there are no distinguishable patterns of the types found by Ivanik (1983). Specimens can be longer than 500 μm. Relatively thick, short oxeas are tabulated separately (Plate 2, Fig. 9). Strongyles (monaxons with rounded ends; Plate 1, Figs. 5-7): Nonspinose strongyles were sporadic at both sites, with a large variation in size and thickness. Acanthoxeas (spinose oxeas; Plate 2, Fig. 2): Sporadic throughout Site 605, relatively more common at Site 604. Lengths vary, but the density of nodes on the spicule is generally rather low. Acanthostrongyles (spinose strongyles; Plate 2, Fig. 4). Monactinal (monaxons rounded at one end and pointed at the other) Styles (no change in thickness at rounded end; Plate 2, Fig. 5, Plate 1, Figs. 2, 3): Common at both sites. Range of variation in size, thickness, and curvature was similar to the oxeas. Tylostyles (one end pointed, the other knobbed; Plate 2, Figs. 3, 6-7). Acanthostyles (spinose styles; Plate 1, Figs. 3, 4). Acanthotylostyles (spinose tylostyles; Plate 2, Fig. 8): some forms had spines only at the knobbed end. "Serrated-spines" (Plate 1, Fig. 1): Associated with the sponge spicules throughout Site 605 was a serrated form originally thought to be poriferan, but since deter-

Siliceous Sponge Spicules from Deep Sea Drilling Project Leg 93