62 
BULLETIN 125, UNITED STATES NATIONAL MUSEUM. 
THALAMOPORELLA BIPERFORATA Canu and Bassler, 1919. 
Plate 6, figs. 10-15. 
1919. Thalamoporella biperforata Canu and Bassler, Geology and Paleontology of the West Indies, 
Bryozoa, Publication Carnegie Institution of Washington, No. 291, p. 88, pi. 6, figs. 10-15, 
Description. —The zoarium is bilamellar. The zooecia are elongate, distinct 
rectangular; the mural rim is thin, salient, bevelled, and bears two hollow tubercles 
on each side of the aperture. The cryptocyst is deep, flat, ornamented with large 
widely spaced pores and with numerous small pores closely placed together; the 
opesiules are very large, far distant from the apertura, placed symmetrically, but 
very unequal in size. The apertura is transverse, oval; the proximal border is 
always concave and the polypidian tube is limited by two small lateral indentations. 
The reticulocellarium is large, quite elongate; its cryptocyst is perforated by two 
opesiules; the opesium bears two lateral denticles serving as pivot to the corneous 
mandible. 
,, . „ . , f ho = 0.10-0. 12 mm. 
Measurements. —Opesium ot zooecium. , . , . 
r [ to = 0.14 mm. 
Zooecium 
Lz = 0.54-0.60 mm. 
lz = 0.34-0.40 mm. 
Opesium of onychocellarium. 
hon = 0.24 mm. 
Ion = 0.12 mm. 
Onychocellarium 
\Lon = 0.90 mm. 
| Ion = 0.30 mm. 
Affinities .—The oral tuberosities are quite variable in size; they are often 
replaced by two fossettes. 
This species is characterized by its onychacellarium, which resembles that of 
Thalamoporella granulata Levinsen, 1909, figured by Osburn, 1914. It differs, 
however, in the very different oval form of its apertura and in the presence of oral 
tuberosities. In its tuberosities this species is quite close to Thalamoporella rozieri 
Savigny-Audouin, 1826. It differs from it in the form of its onychocellarium pro¬ 
vided with two opesiules, which are not figured by Levinsen in the numerous draw¬ 
ings which he has given. 
Occurrence .—Lower Miocene (Bowden horizon): Cercado de Mao, Rio Cana and 
Rio Gurabo, Santo Domingo; and Bowden, Jamaica (common). 
Cotypes. —Cat. No. 68483, 68484, U.S.N.M. 
Family STEGANOPORELLIDAE Levinsen, 1909. 
Genus STEGANOPORELLA Smitt, 1873. 
(For description see Bulletin 106, U. S. National Museum, p. 259.) 
STEGANOPORELLA PARVICELLA Canu and Bassler, 1919. 
Plate 6, figs. 6-9. 
1919. Steganoporella parvicella Canu and Bassler, Geology and Paleontology of the West Indies, 
Bryozoa, Publication of the Carnegie Institution No. 291, p. 89, pi. 6, figs. 6-9. 
Description .—The zoarium is unilamellar incrusting algae or bryozoa. The 
zooecia are distinct, elongate, separated by a shallow furrow; the mural rim is thin, 
