518 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Genotype. — Porina probosdidae Waters, 1889. 
Range. — Jacksonian — Recent. 
This genus is zoarial; no special distinct zooecial function separates it from 
IlasweTlia. Nevertheless, it has some important zoarial functions 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. 
SEMIHASWELLIA TRIPORA, new species. 
Plate 66, figs. 24-27. 
Description. — The zoarium is free, somewhat compressed, not branched, bear- 
ing laterally large apophyses quite salient ; there are three longitudinal rows of 
zooecia indicated on the dorsal by as many rows of small round avicularia. The 
zooecia are small, indistinct; the frontal is a tremocyst with sulci. The peristome 
is quite salient, perpendicular to the zooecial plane, thin and garnished with two 
small distal avicularia, almost symmetrical; the peristomice is orbicular. The 
spiramen is a small pore placed just below the peristome, not salient. 
M easurements . — P eristom i ce 
f Ape— 0.05 mm. 
\lpe= 0.05 mm. 
Zooecia. — L 2=0.35-0.40 mm. 
Affinities. — This species differs from Semihasioellia exilis in its very salient 
peristome and in its much shorter zooecia, less than 0.50 mm. 
Occurrence. — Middle Jacksonian: Near Lenuds Ferry, South Carolina (rare). 
Cotypes. — Cat. No. 64167, U.S.N.M. 
SEMIHASWELLIA EXILIS, new species. 
Plate 66, figs. 11-23. 
Description. — The zoarium is free, cylindrical, thin , formed of three longitudi- 
nal rows of zooecia opening on only one side ; it often bears laterally some cylindri- 
cal hollow appendages. The zooecia are indistinct ; the frontal is confused with the 
zoarial surface; it is formed of a thick tremocyst with tubules, placed on a perfo- 
rated olocyst; the dorsal is of the same construction and bears a small round 
salient avicularium without pivot. The peristome is salient, thin, almost perpen- 
dicular to the zooecial plane; the peristomice is orbicular. The spiramen is small, 
not salient, and placed on the median axis of the zooecium immediately below the 
peristome. 
Measurements. — Peristomice Zooecia. — Z, 3=0.45-0.50 mm. 
|ype=0.05-0.07 mm. 
Variations. — The peristome quite often bears two small avicularia symmetri- 
cally placed (fig. 15). The sulci (figs. 15, 16) do not always appear with clearness 
on our fossils (figs. 12, 14) ; these are the A^ery fragile ornaments which fossiliza- 
tion much attenuates. 
We have made numerous longitudinal sections without ever discovering the 
ovicell ; the 50 specimens observed have shown none of them visible, exteriorly as 
