34 BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 



ACANTHODESIA OBLONGULA Ulrich and Sassier, 1904. 



Plate 10, figs. 1-3. 



1904. Membranipora ohlongula Ulrich and B.^sslbr, Bryozoa, Mar>'land Geological Siirvey, 

 Miocene, p. 407, pi. 110, figs. 2-5. 



Description. — The zoarium incrusts shells. The zooecia are distinct, separated 

 by a furrow of little depth, elongated, rectangular; the mural rim is rounded, regular, 

 granular, ornamented by two large distal tubercles. The opesium is entire, elliptical, 

 finely denticulated and provided with spicules of greater or less length. 



f^o = 0.40mm. „ . fL2 = 0.45-0.50 mm. 



' lo = 0.15 mm. °^^^^( Z2 = 0.25-0.30 mm. 



Measurements. — Opesia , r.\ r „_ Zooeciaj 



Variations. — The figures of Ulrich and Bassler are incomplete as the tubercles 

 have not been restored fully enough. On Plate 10 we reproduce a better photograph 

 of the type (fig. 1). Sometimes the tubercles are joined and form a single large 

 distal tuberosity (fig. 2). The micrometric measurements vary according to the 

 specimens and even on the same specimen they are irregular. The zooecia giving 

 rise to a new series are larger according to the rule in the'genus. 



Affinities. — This species differs from Membranipora fiabellata Canu, 1904, in 

 the presence of spicules and in the larger micrometric measurements. It differs 

 from AcantJiodesia savarti Audouin, 1826, in the presence of large distal tubercles. 



Occurrence. — Miocene (Calvert formation) : Plum Point, Reeds, and Chesapeake 

 Beach, Maryland (common). Miocene (Chop tank formation): Jones wharf, Paw- 

 paw Point, Dover Bridge, etc., Maryland (rare). 



Plesiotype.— Cat. No. 68433, U.S.N.M. 



ACANTHODESIA RECTANGULARIA, new species. 



Plate 9, fig. 11. 



Description. — The zoarium incrusts oyster shells. The zooecia are distinct, 

 elongated, rectangular; the mural rim is thin, sahent; the cryptocyst is deep, 

 short, a little convex. The opesium is large, oval, terminal. 



ir 4 r\ • f^o = 0.35mm. „ . fZ2 = 0.50-0.55 mm. 



Measurements. — Opesia , Zooecia , « ^r, ^n or 



^ [lo = 0.20 mm. [ Iz = 0.30-0.35 mm. 



Affinities. — On certain isolated zooecia we have been able to observe some 

 spines, and even traces of the serrate proximal denticle. In spite of appearances 

 of our figure, which is incomplete because of the disappearance of the spines, this 

 species belongs really to the genus AcantJiodesia. It is well characterized by the 

 rectangular form of its zooecia. 



Occurrence. — ^Miocene (Yorktovra formation) : 3 miles southwest of Petersburg, 

 Virginia (rare). 



nololype.—C&t. No. 68434, .U.S.N.M. 



