EXOGYKA PONDEROSA ZONE. 



29 



MORTONICEB.AS SUBZONE. 



Seventy-two species, questionably 75, are known from the Mortoniceras subzone. These 



are as follows : ' 



Fossils from Mortoniceras subzone. 



Echinoderinata : 



Cassidulus subquadratus Conrad, a c. 

 Vermes : 



Serpula sp. (nearly straight tube), a c. 



Hamulus onyx Morton, a b c. 



H. squamosals Gabb. a b c. 



H. major Gabb. a b e. 

 Mollusca: 



Nucula percrassa Conrad, abed. 



N. eufalensis Gabb. a c. 



N. sp. (cf. sp. nov. from Snow Hill. N. C). 6 c. 



Leda longifrons Conrad, a b c. 



Perrisonota protexta Conrad, a c. 



Cucullsea carolinensis (Gabb). b c. 



Breviarea umbonata (Conrad), c. 



Nemodon sp. nov. b e. 



Barbatia lintea Conrad. 6 c. 



Gervilliopsis ensiformis (Conrad), a b c. 



Perna sp. nov. (found at Broken Arrow Bend, Ala.- 

 Ga., etc.). c d. 



Ostrea plumosa Morton, a b c. 



O. tecticosta Gabb. ab c. 



O. cretacea Morton, c d. 



0. diluviana Linnseus. e. 



0. panda Morton, a b e. 



O. sp. nov. (first found at House Bluff, Ala.), c d? 



0. sp. nov. (also found at Blue Banks Landing, N. C. 

 etc.). b e. 



O. sp. nov. (from near Hatehechubbee, Ala.), e. 



Grypheea aucella Roemer. b c. 



Exogyra ponderosa Roemer. b e. 



E. ponderosa var. erratieostata Stephenson, b c. 



Trigonia eufalensis Gabb. a e. 



Pecten quinquecostatus Sowerby. a b c. 



P. argillensis Conrad, a b? c? 



P. simplicius Conrad, ab c. 



P. burlingtonensis Gabb. b c. 



P. sp. nov. c d. 



Lima reticulata Forbes, a b e. 



L. pelagica (Morton), a e? 



Anomia argentaria Morton, a b c. 



Mollusca — Continued. 



Anomia sp. nov. (also found at Snow Hill. N. C. etc 



bed. 

 Cymella bella Conrad, ab c. 

 Liopistha alternata Weller. c. 

 L. sp. (aff. L. alternata "Weller). e. 

 Veniella conradi (Morton), ab e. 

 Etea carolinensis Conrad, abed. 

 Vetericardia crenalirata (Conrad), a c. 

 Crassatellites carolinensis Conrad, bf c? 

 Radiolites austinensis Roemer. b c. 

 Arena carolinensis Conrad, c. 

 Lucina glebula Conrad, bf c. 

 Tenea pinguis (Conrad), a c. 

 Cardium eufaulense Conrad, ab c. 

 C. spillmani Conrad, ab c. 

 Cardium alabamense Gabb. a c. 

 Cyprimeria depressa Conrad, abed. 

 Cyclotliyris alta Conrad, b c. 

 Legumen planulatum (Conrad), a b e. 

 Linearia metastriata Conrad, a c. 

 Leptosolen biplicata (Conrad), abed. 

 Cymbophora lintea (Conrad), abed. 

 Schizodesma appressa Gabb. ab c. 

 Corbula crassiplica Gabb. a b e. 



C. carolinensis Conrad, bed. 

 Dentaliurn ripleyanum Gabb. ab e. 



D. sp. nov. a c. 



Cadulus obnutus (Conrad), a c. 



Lunatia obliquata Meek and Hayden. ab c. 



Gyrodes abyssina (Morton), a e. 



G. crenata Conrad, ab c. 



Turritella trilira Conrad, ab c. 



T. quadrilira Johnson, b c. 



Nautilus sp. nov. (large), c. 



Baculites anceps Lamarck? e. 



B. asper Morton, b e. 



Placenticeras planum Hyatt, c. 



P. guadalupae (Roemer). c. 



Mortoniceras sp. (aff. texanum (Roemer)). c. 



Hamit.es torquatus Morton, c. 



Of the species listed 12, questionably 13, are restricted to the Mortoniceras subzone; 10, 

 questionably 11, range downward into the basal beds of the Eutaw formation; 43, questionably 

 44, range up into the part of the Exogyra jjonderosa zone above the Mortoniceras subzone; 40 of 

 the 72 occur in the Exogyra costata zone. Two known to be present in higher horizons are 

 questionably present in the Mortoniceras subzone. Crassatellites carolinensis Conrad and Cor- 

 bula carolinensis Conrad, though questionably identified, belong to types not known to range 

 above the zone of Exogyra -ponderosa and are here treated as correctly identified. 



Of the 13 restricted species 2 occur in the marine invertebrate-bearing beds forming the 

 upper part of the Black Creek formation of the Carolinas, and none are known in the overlying 

 Peedee sand of that region. Of the 13 restricted species, 1, Liopistha alternata Weller, occurs 

 in New Jersey, where it is confined to the Merchantville clay marl which forms the base of the 

 Matawan group. The genus Mortoniceras, which is represented in the eastern Gulf region by 



la, Exogyra costata zone; 6, Exogyra ponderosa zone above the Mortoniceras subzone; c, Mortoniceras subzone; i, basal beds of Eutaw formation. 



