140 
BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 
of the avicularia is one of the most tantalizing problems of bryozoology. It will 
remain unsolved until we know the exact physiological functions of these organs. 
The apertura has no fixed measurements; it may be elongate or transverse, 
large or small. It appears to be in rapport with the size of the zooecium itself. 
The ancestrula is very small; it is reduced to its apertura; it engenders four normal 
zooecia and a zooeciule bearing only a salient median avicularium. The presence 
of the median avicularium is a vital necessity for the zooecium and the first bud 
of the ancestrula is really this avicularium. The specimens from the Pliocene are 
still more irregular than those of the Miocene. 
Affinities .—This species differs from Aimulosia brevis in its large micrometric 
dimensions and in the presence of areolar pores. It differs from Aimulosia radiata 
in its greater zooecial width, in the absence of interareolar costules, and in the 
much smaller areolar pores. 
Occurrence .—Miocene (Duplin marl): Wilmington, North Carolina (rare); 
Harvey’s Mills, Leon County, Florida (rare); and Muldrow’s Mills, 5 miles south of 
Maysville (rare), South Carolina. Pliocene (Waccamaw marl): Waccamaw River, 
Horry County, South Carolina (rare). 
Cotypes.— Cat. Nos. 68629, 68630, U.S.N.M. 
AIMULOSIA BREVIS, new species. 
Plate 3, figs. 5-7. 
Description .—The zoarium incrusts shells. The zooecia are distinct, separated 
by a furrow, ovoid, very short; the frontal is convex, smooth, generally without 
areolar pores, terminated on the median line by a small, round, very salient 
avicularium. The apertura is semielliptical; the peristome is little salient, wide, 
and bears two hollow spines. The ovicell is globular, salient, smooth, transverse 
with a very large orifice. Frequently there is a triangular avicularium at the side 
of the peristome. 
,, . . fk=0.08mm. „ . 1X2 = 0.30 mm. 
Measurements. —Apertura, 7 .. Zooecia;, . 
1 lla = 0.08 mm. Uz =0.20 mm. 
Affinities .—The areolar pores are very small; they are easily closed by 
fossilization and the zooecia appear deprived of them. 
This species differs from Aimulosia aculeata in its smaller micrometric 
measurements and in the apparent absence of areolar pores. 
Occurrence .—Pliocene (Caloosahatchee marl): Shell Creek, De Soto County, 
Florida (rare). Lower Miocene (Bowden marl): Bowden, Jamaica (common). 
Lower Miocene (Bowden horizon): Cercado de Mao, Santo Domingo (rare). 
Cotypes.— Cat. Nqs. 68631-68633, U.S.N.M. 
, AIMULOSIA RADIATA, new species. 
Plate 32, fig. 5. 
Description .—The zoarium incrusts shells. The zooecia are distinct, separated 
by a furrow, elongate, claviform; the frontal is convex, garnished laterally with 
large areolar pores and with interareolar costules arranged in radiating rows, and 
formed of a pleurocvst, slightly granular, surmounting a smooth olocyst; the 
median avicularium is very salient, oblique, and surmounts a mucro. The apertura 
is semilunar, located at the base of a short peristomie. The peristome is thick 
and bears two hollow spines. The ovicell is globular, very salient, smooth, very 
widely open before the median avicularium. 
