Bulletin - United States National Museum - Smithsonian Institution

58 BULLETIN 96, UNITED STATES NATIONAL MUSEUM.
convexity of the frontal ;
they are quite apparent when the prepara-
tion is properly inclined.
The spiramen is little visible in perspective because it is in a plane
almost perpendicular to the zooecial plane.
Occurrence.—Lower Jacksonian: Jackson, Mississippi (rare).
Ty2)e.—C^t. No. 62603, IJ.S.N.M.
Genus HASWELLIA Busk, 1884.
1SS4. Hafiicellia Busk, Report on the Polyzoa collected l^y H. M. S.
Challcnyer, pt. 1, p. 171.
The apertura has its proximal border notched by a very wide
rimule not separated from the anter. The frontal is a very thiclc
tremocyst. The spiramen is a small salient tube. The zoarium is
cylindrical.
Genotype.—Jlaswellia {Myrlo2oum) austraUensis Haswell, 1880.
Range.—Tongrian-Recent.
SEMIHASWELLIA, new genus.
The zooecia are disposed only on one side of the zoarium; the
dorsal bears only avicularia. The frontal and the dorsal are of the
same nature and are formed of a tremocyst with sulci.
Genotype.—Porina prohoscklea Waters, 1888. Range : Jacksonian-
Recent.
This new genus is zoarial; no distinct zooecial function separates
it from Haswellia. Nevertheless it has some important zoarial func-
tions susceptible of giving generic characters; the very constant
presence of small dorsal avicularia seems to be a very good character.
The recent specimens are extremely rare and it is still not possible
to study them in detail. Species of both flaswellia and Semihas-
wellici occur in the Jacksonian of the Southern States.
Genus GIGANTOPORA Ridley, 1881.
1881. Gigantopora Ridley, Zoological collections made din-ing survey of
H. M. S. Alert. Proceedings Zoological Society London, p. 47.
The apertura bears a rimule. The frontal is an olocyst. The
spiramen is inconstant; it is almost as large as the apertura.
Genotype.—Gigantopora lynchoides Ridley, 1881.
Range.—Jacksonian-Recent.
Genus GEPHYROPHORA Busk, 1884.
1884. Gephyrophora Busk. Report on the Polyzoa collected by H. M. S.
Challenger, pt. 1, p. 67.
The apertura nears a proximal rimule. The frontal is a tremocyst.
Genotype.— Gephyrophora polyniorpha Busk, 1884.
Range.—Tongrian-Recent.