404 SYSTEMATIC PALEONTOLOGY 



depth of the valve increase, while the amount of sculpture decreases with 

 the eccentricity of the apex. There is such complete gradation through- 

 out the series that the separation of two species seems impossible. The 

 individuals from the Calvert formation appear to be almost or quite 

 restricted to the typical form. In the Choptank formation where the 

 species attains its maximum development there is extreme variation in 

 form. The St. Mary's formation has 3delded few specimens. It will be 

 in material from this formation, and probably in Virginia or the 

 Carolinas, that multilineata will, if ever, be recognized as a valid species. 



Length, 25 mm.; width, 25 mm.; height, 6.5 mm. 



Occurrence. — St. Mary's Formation. Cove Point, near Great Mills. 

 Choptank Formation. Jones Wharf, Governor Eun, 2 miles south of 

 Governor Eun, Pawpaw Point, Turner, St. Leonard Creek, Trappe 

 Landing, Dover Bridge, Cordova, Peach Blossom Creek. Calvert For- 

 mation. Chesapeake Beach, 3 miles south of Chesapeake Beach, Tru- 

 man's Wharf, Lyon's Creek, Fairhaven. 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum, Philadelphia Academy of Natural Sciences, 

 Cornell University. 



Class BRYOZOA Ehrenberg. 



Order CYCLOSTOMATA Busk. 



Family IDMONElDy^ Busk. 



Genus IDMONEA Lamouroiix. 



Idmonea(?) expansa n. sp. 



Plate CIX, Figs. G, 7, 8. 



Descriptio7i. — Zoarium adnate, beginning with a single "zooecium to 

 which others are added rapidly until an irregular flabellate expansion is 

 produced that with further growth becomes more or less lobate. In the 

 older examples the lobes are seen to be due to the development of the 

 zooecia in systems composed of two pinnate series of transverse rows 

 springing alternately from the opposite sides of a zigzag or wavy median 

 line. In the rows tho zooecial apertures, which are rounded quadrate in 



