STORTH AMEBICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 139 



As our single specimen is without an ovicell, the generic determination must 

 remain doubtful. This species is named in honor of Mr. Wendell C. Mansfield, 

 of the United States Geological Survey, who has collected many interesting 

 specimens of bryozoa for our study. 



Occurrence. — Miocene (Yorktown formation): H miles southwest Reed's 

 Ferry, Virginia (very rare). 



Holotype.— Cat. No. 68627, U.S.N.M. 



CYCLICOPORA(?) GIGANTEA, new species. 



Plate 37, fig. 5. 



Description. — The zoariimi incrusts pebbles. The zooecia are distinct, 



gigantic, ogival or hexagonal; the frontal is convex and formed of a tremocyst 



^vith small scattered pores surmounting an olocyst perforated by very minute 



pores corresponding to the tremopores. The apertura is elongate, elliptical, without 



lyrule or cardelles, with a concave proximal border; it is surroxmded by a salient 



peristome, more or less thick and widened. The ovicell is hyperstomial, not 



embedded in the distal zooecium. 



^ , ^ f^a= 0.30-0.35 mm. ^ . fZ2= 1.50-1.60 mm. 



Measurements. — Apertura^, _ „_ _ „. Z,ooccia^, „„ , Ar\ ^-^ 



^ iZa = 0.30-0. 3£) mm. Ite =0.90-1.40 mm. 



Variations. — The micrometric measurements are variable. The tremocyst is 

 detachable and finely granular between the pores. The ovicells of our specimens 

 are broken and we are therefore unable to classify the species without doubt. 



Occurrence. — Pleistocene: Santa Monica (Tremochal Canyon), California (rare). 



Holotype. —Ca,t. No. 6S628, U.S.N.M. 



Genus AIMULOSIA JuUien, 1888. 



(For description, see Bulletin 106, U. S. National Museum, p. 428.) 



AIMULOSIA ACULEATA, new species. 



Plate 21, figs. 10-14. 



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



by a furrow, ovoid, wide; the frontal is convex, smooth, perforated laterally by 



small, scattered, areolar pores; it bears on its median line a small avicularium 



very salient, oblique, orbicular, without pivot. The apertura is semilunar, a little 



elongate, with a somewhat concave proximal border; the peristome is thick, 



little salient, and garnished by two distal spmes. The ovicell is globular, smooth, 



quite salient, transverse, very widely open in front of the median avicularium. 



Frequently there is a small triangular avicularium at the side of the apertura. 



f^a = 0.10mm. „ . jXz = 0.50mm. 



Measurements. — Apertura, „,„ /.ooeciau «^k„„, 



^ Ua =0.10 mm. Uz =0.4o mm. 



Variations. — In all the species of this genus there is a very great micrometric 

 difference between the anccstrular zooecia and the marginal ones. Our measure- 

 ments are the largest that we have observed. The oral avicularium replaces an 

 areolar pore. This is the rule in all the cheilostomatous Bryozoa. This organ is 

 nourished in fact from the interior of the zooecia and must necessarily be in 

 relationsliip with the mesenchymatous tissue. This avicularium is inconstant in 

 its presence; sometimes it is lacking; sometimes there are two. The irregularity 



