MOLLUSCA 



138 



I 



Fig. 5 a, Chemnltzia gabiieli, height 5.25 mm; b, Chrysallda alveata, height 4 mm; c, Evalea denaestriata, height 12 mm; 

 d, PyrguHna densecostata, height 2.5 mm; e, Chiysalida alveata, 4 mm; f, Ringicula doleari, height 1.75 mm; g, Haloa 

 japonica, height 5 mm; h. Pupa sp. 8 mm; i, Nakagamigawaia spiralis, height 4 mm; j, Adamnestia japonica, height 8 mm; 

 k, Eocylichna soyae. height 10 mm; I, Coleophysis minima, height 3 mm; m, Cylichnatys angustata, height 5 mm. 



and Leupold and van der Vlerk (1931). Mollusks are rare 

 and poorly represented in limestones of late Eocene age 

 (Tertiary b) that form the near-basement pavement and 

 include only poorly preserved valves of Pecten and Area, 

 minute turbinids, molds of small gastropods, and one iden- 

 tifiable mollusk, a species of Turritella related to a living 

 sfjecies also repwrted from the upper Tertiary of Indonesia 

 (Ladd, 1966). In what is questionably considered early Oli- 

 gocene, three shells of Rissoina ailinana Ladd, 1966 and 

 nine specimens of the naticid Ampullina berauensis 

 described from the Miocene of East Borneo (Ladd, 1966) 



are represented. Above the early limestones are 610 m 

 (2000 ft) of fossil reef of Miocene age which contain the 

 bulk of the Enewctak fossil record, about 170 species. The 

 post-Miocene sections consist of more than 183 m (600 ft) 

 of consolidated limestone and about 9 m (30 ft) of uncon- 

 solidated sediments (Ladd, 1966) from which 105 species 

 are refxarted. 



Paleoecology 



Reef-associated limestones that underlie Enewetak do 

 not record slow, continuous subsidence but rather periods 



