Maryland Geological Sukvey 501 



Description. — " Elevated subglobose. Spire rather high ; whorls four, 

 rounded, abruptly truncated or concave above. Body whorl gibbous. 

 Mouth broad, rounded. Umbilicus (in casts) small, perforated rather 

 deeply. No markings on the casts. Length 0.8 in., width of body whorl 

 O.r in., length of mouth 0.6 in."— Gabb, 1863. 



Type Locality. — New Jersey. 



The species is known in Maryland only in the form of poorly preserved 

 casts characterized by tabulated shoulders, angular shoulder keel, well 

 rounded body and very small umbilicus. 



The very small umbilical area and pit indicate Euspira rather than 

 Gyrodes. 



Occurrence. — Matawan Formation. Arnold Point, Severn Eiver, 

 Anne Arundel County. Monmouth Formation. ? Brightseat, Prince 

 George's County. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey. 



Outside Distribution. — Matawan Formation. Merchantville clay marl, 

 New Jersey. 



Family EUOMPHALIDAE 



Genus DISCO HELIX Dunker 



[Palseont. ser. I, vol. i, 1847, p. 132] 



Type. — Discohelix calculiformis. 



Shell discoidal, depressed, the apical surface flattened or slightly con- 

 cave, the dorsal surface widely umbilicate; whorls rectangular in cross- 

 section, the peripheral keels acute and either simple or nodulose ; aperture 

 quadrate. 



The classification of these depressed, turbinate and discoidal forms is 

 very uncertain. The typical Paleozoic Euompltalidve are separated from 

 the typically Tertiary and Eecent Solariida on the characters of the 

 nucleus which in the former is dextral and in the latter sinistral. Both 

 families are represented in the Mesozoic, and rarely by specimens which 

 have preserved their nuclei. For that reason the systematic work upon 

 these groups has been unusually difficult and unsatisfactory. 



Etymology: Sio-kos, disc; eXi£. spiral. 



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