NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 183 



expanded above, contracted below the middle, where there is a small denticle on each side, and nearly 

 straight or curved slightly outward on the lower side ; peristome simple, not elevated. Surface punctate 

 excepting over a space just beneath the orifice that is smooth and elevated into a conical or obtuse umbo. 

 A\-icuIaria of two kinds and sizes, both sets very irregularly distributed. Those of the smaller set are 

 ovate and less than half the size of the zooecial orifice, and situated in one of the corners of a zooecium; 

 those of the larger set occupy each the place of a zooecium, have a triangular or acuminate ovate aperture 

 considerably larger than the zooecial orifice, and have the pointed end or side strongly elevated. Ovicells 

 immersed, somewhat smaller than the zooecia, convex, smooth centrally, punctate marginally, often 

 with an eccentric, smooth oval space distinguished from the rest of the surface by an impressed line. 



Further study of the types and other specimens show that the original descrip- 

 tion is perfectly exact. The aperture measures about 0.12 mm. by O.OS mm. 

 The frontal is garnished wath a double row of areolar pores and with a detachable 

 pleurocyst. Between the apertures there is sometimes a very small, roimd, non- 

 salient avicularium. The large interzooecial avicularium is very characteristic, 

 but it is rather rare. 



The zoarium developes into large nodose masses on gastropod shells. Celle- 

 pora minuta shows the same phenomenon of symbiosis and, although its other 

 characters are close, its zooecia are also small and of such a kind that it is very 

 difficidt to distingush the two species. The present species differs, however, from 

 Cellepora minuta in the absence of the small, very salient avicularium arranged 

 between the apertures and by the great frequency of the double row of areolar 

 pores. Moreover, the zoarium is larger and more spinous than that of Cellepora 

 minuta. We have not yet discovered the ovicell. 



Occurrence. — Miocene (Calvert formation) : Plum Point and other localities in 

 Maryland (common). Miocene (Yorktown formation): Yorktown, Virginia (rare). 

 Miocene (Choctawhatchee marl)-: Jackson Bluff, Ocklocknee River, 25 miles south- 

 west of Tallahassee, Florida (verj' rare). Miocene (Duplin marl): Harvey's Mills, 

 Leon County, Florida (very rare). Natural Well, 2 miles southwest of Magnolia, 

 Duplin County, North Carolina, and Muldrows Mills, 5 miles south of Maysville, 

 South Carolina (rare) . 



Cotypes and Plesiotype. —C&t. Nos. 68716-68720, U.S.N.M. 



CELLEPORA CRIBROSA Ulrich and Bassler, 1904. 



Plate 25, fig. 8. 



1904. Cellepora cribrosa Ulrich and Bassler, Maryland Geological Survey, Miocene, p. 429, pi. 

 117, figs. 5, 6. 



The original description by Ulrich and Bassler is as follows: 



Zoarium forming small irregular compressed masses. Zooecia ven,- irregularly disposed, some erect, 

 others prostrate, 0.5 mm. to 0.7 mm. long by 0.4 mm. to 0.6 mm. wide; surface strongly punctate; orifice 

 rounded, the normal form showing a slight constriction a little below the middle, where a small tooth 

 projects into the cav-ity from each side; peristome thick and more or less elevated, ringlike. A\-icu- 

 laria of moderate size, more or less acuminate ovate," attached to and projecting beyond tlie plane of 

 the inferior side of the peristome; rarely absent. 0\-icells few, known only in the broken condition 

 in which they appear as deep semicircular excavations in front of the zooecial orifices. 



Only the type specimen of this species has so far been discovered and we are 

 unable to add anything to the original description or to place the species more ac- 

 curately generically, 



Occurrence. — Miocene (Calvert formation): Reeds, Mar^dand (very rare). 



Holotype.— C&t. No. 68721, U.S.N.M. ' ' • 



