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. 

 Theancestrulais 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 anccstrula is really tliis avicularium. The specimens from the Pliocene are 

 still more irregular than those of the Miocene. 



Affinities. — This species differs from Aimulosia hrevis 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 ax'eolar 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.—C&t. 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. 



,, .. A i fAa = 0.08mm. „ . fi2 = 0.30mm. 



Measurements. — Apertura, „ „„ Zooeciai, „ „. 



^ Ua =0.08 nmi. 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 Coimty, 

 Florida (rare). Lower Miocene (Bowden marl): Bowden, Jamaica (common). 

 Lower Miocene (Bowden horizon): Cercado de Mao, Santo Domingo (rare). 



Cotypes.—C&t. Nos. 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 pleurocyst, 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. 



