398 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
because lie must draw on his personal experience for the positive elements of appre- 
ciation. 
Affinities. — The species differs from Hippo dip! osia magniporosa , in which the 
zoarium is also unilamellar, in the greater length of its apertura and zooecium, 
chiefly in the presence of the median peristomial avicularium. 
0 ccurrence.- — Vicksburgian (Marianna limestone) : West bank of Conecuh 
River, Escambia County, Alabama (very rare) ; Murder Creek, east of Castlebury, 
Conecuh County, Alabama (rare) ; near Claiborne. Monroe County, Alabama (rare). 
Vicksburgian (By ram marl) : By ram, Mississippi (very rare.) ; Vicksburg. 
Mississippi (rare in the upper beds). 
Cotypes. — Cat. Nos. 64280, 64281, TJ.S.N.M. 
Genus HIPPOZEUGOSELLA Canu and Bassler, 1917. 
1917. Ilippozeugosella Canu and Bassler, Synopsis of American Early Tertiary Cheilostome 
Bryozoa, Bulletin 96, United States National Museum, p. 42. 
The ovieell is liyperstomial, its orifice is large, without rapport with the oper- 
culum, and is closed by a special membrane. The aperture is elliptical; two small 
cardelles separate the anter from the somewhat smaller poster. The frontal is a 
tremocyst with small pores. The zoarium is free; the zooecia are joined two by 
two. No spines. Avicularia present. 
Genotype.- — H ip pozeugo sella ( Bactridium ) hagenowi Reuss, 1847. 
Range. — Priabonian-Miocene. 
The only species known are Bactridium hag enow i Reuss, 1847, of the Priabonian 
and Cucullipora tetrasticlia MacGillivray, 1895, from the Miocene. 
This genus embraces the two ancient genera Bactridium Reuss, 1869, and 
C ucullipora MacGillivray, 1895, with limits still more extended. 
Bactridium was created in 1847 by Reuss with unilamellar and biserial species. 
The first three species belong to Bcrupocellama. Again, in 1869, he maintained his 
genus, but with Bactridium liagenowi Reuss, 1847, as a type and with a definition 
based upon the zoarium. In 1891, Waters in studying this species discovered that 
it had a schizoporellidan aperture. It is very difficult to establish the limits be- 
tween the schizoporellidan and hippoporinan apertures in the fossil forms. 
The genus Cucullipora MacGillivray, 1895, embraces the bilamellar and biserial 
species in which the orifice is provided with labial processes. The inconstance of 
the latter does not permit them to be considered as generic characters. They occur 
in other genera, such as Watersipora, Lagenipora, etc. 
In the American Tertiary Ave have one unilamellar, biserial species. Five 
other species are bilamellar and biserial; the edge of the two lamellae is visible 
laterally with a very characteristic aspect. This edge is hidden in a single species 
( Iiippozeugosella sexordinata) by the addition of two supplementary rows. In 
all these species the mode of ramification is identical. Each new branch is formed 
by the union of two zooecia arising from two consecutive zooecia (pi. 53, fig. 4). 
Finally, the mode of gemmation and of the pairing of zooecia reminds one of 
C atenicella Audouin, 1826, Ichthyaria Busk, 1884, and TJrceolipora MacGillivray, 
