era, including Meyncina termieri Hottinger, Haurania amiji Henson, H. deserta Henson, Involutina sp., Trochol- ina sp., and Frondicularia sp., are common elements (see Fugagnoli and Loriga Broglio, 1996, for a review). The cod- iacean algae Palaeodasycladus mediterraneus (Pia) and Thaumatoporella parvovesiculi fera (Raineri) are prevalent in Tethyan facies associated with Lithiotis and Cochleari tee. The rhodophyte Cayeuxia sp. is found in association with Li thioperna scutata.

In Oregon, the interbuildup area supports a wide array of microfossils including red algae, small miliolid forami- nifera, thin-shelled ostracodes, and possibly Palaeodasy cladus sp. The Cow Creek and Jackass ranch sites are par- ticularly rich in algae.

Intensity of Bioerosion and Encrustation

Entobia (clionid borings) can be seen on individual Lith iotis specimens in thin section and on hand samples. The limpet Scurri a was found in the Assemsouk structure on a Coehlearites valve (Lee, 1983) and a shallow ovoid exca- vation, similar to the resting trace of a limpet, was found on the interior of a transported Lithiotis Tryp.anites shaped borings without calcareous linings, possibly the re- sult of boring by lithophagid bivalves, were found on a few Lithiotis specimens from the northern Italian sites. Sev- eral disarticulated lithophagid valves were found in the interbuildup facies of the Robertson Formation in Suplee- Izee. Many of the algae and Lithiotis problematica were encrusted by serpulid worms in the Calcari Grigi. Most en- crustation occurs on the interiors of disarticulated lithio- tid shells and therefore is post-mortem.

Bioerosion is conspicuously absent on the valves of Ger villeioperna sp., Mytiloperna sp., and Lithioperna scutata. The exclusion of bioeroders from estuaries, lagoons, bays, and intertidal zones has been well documented by the modern aquaculture industry (see White and Wilson, 1996, for a review). Similar restrictions may have occurred in intertidal and fresh-water influenced paleoenviron- ments of the Early Jurassic. Modern coral reefs, particu- larly reefs in mesotrophic waters, are eroded continuously by a host of bioeroding organisms (Hallock and Schlager,