NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
91 
Variations .— The aborted zooecia are closed with a median pore. The ances- 
trula is elliptical and very small. The gymnocyst is more developed on the zooecia 
close to the ancestrula; here, the frontal tuberosity is absent and the difference from 
Electra is indistinguishable. The characteristic interopesial cavities are developed 
far from the ancestrula on the wider parts of the zoarium. 
Affinities . — This species differs from C onopeam lioockeri Haime, 1850, in its 
much smaller frontal tuberosity and in its wider mural rim. 
It differs from Conopewn concavum in its convex gymnocyst, and its mural 
rim less enlarged at the base and not concave. 
Occurrence .— Lower Jacksonian (Moodys marl) : 24 miles north of Robert, 
Newton County, Mississippi (rare). ' 
Ilolotype. — Cat. No. 63868, U. S. N. M. 
CONOPEUM HOOCKERI Haime, 1850. 
Plate 19, figs. 8-10. 
1850. Membranipora lioockeri Haime in D'Archiac’s Description des animaux fossiles du 
groupe nummulitique de l’lnde, Memo ires Societe Geologique France, ser. 2, vol. 3, p. 227, pi. 36, 
fig. 5. 
1869. Membranipora lioockeri Reuss, Die fossilen Antliozoen und Bryozoen der Schichten- 
gruppe von Crosaro, Denkscliriften der k. Akademie der Wissenschaften, Wien, vol. 29 p 40 p] 
36. fig. 14. ’ 
1891. Membranipora lioockeri Waters, North Italian Bryozoa, Quarterly Journal Geological 
Society, London, vol. 47, p. 13. 
Description . — The zoarium incrusts shells. The zooecia have a marked luster 
and are distinct, elongate, elliptical, somewhat narrowed posteriorly; the mural 
rim is very thin, and sharply outlined, little enlarged at the base ; the gymnocyst is 
very convex. The opesium is regular in outline and elliptical. The interopesial 
cavities are fusiform but rarely developed. The dorsal bears two distal impressions 
which are excavated in the substratum. There is a distal septula and two septulae 
are on each lateral wall. 
Measurements . — Opesia 
1 7i,o—0.30-0.Sl mm. 
\lo= 0.18—0.20 mm. 
Zooecia 
)Z2=0.36-0.38 mm. 
U;s=0.24 mm. 
Affinities . — We have been unable to find Haime’s original specimens in the 
Museum of Natural History of Paris and verify the determination of Reuss. 
There are some differences between our specimens and Reuss’s figure which does 
not indicate a hump-like, very constant gymnocyst, and in which no interopesial 
cavities are shown. Moreover, Waters indicates an opesium 0.35 mm. long, whereas 
our own specimens measure only 0.31 mm. These are slight differences, and it 
would be ridiculous to form a new species for four one-hundredths of a millimeter. 
On the other hand, the species is quite variable itself. The hump-like gymno- 
cyst which is its fundamental characteristic, is often little developed and some- 
times suppressed entirely ; again, the zooecia are not always separated by a furrow 
and the neighboring mural rims are closely adjacent. 
