NORTH AMKKU'AX KARLY TERTIARY BRYOZOA. 87 



CONOPEUM ORNATUM. new species. 



Plate 3, t\. 2. 



Description. Zoarium bihiniinato. The zooecia are distinct but separated by 

 a common elevation. The mural rim is somewhat rounded and almost everywhere 

 of equal breadth. The opesium is median and elliptical. The interopesial cavities 

 are distinct and irregular. 



Afliniti, \. The <>rn<iiii< ntution of its surface renders this species absolutely 

 characteristic, although this feature is reproduced sometimes in other species, but 

 only accidentally. Unfortunately we possess but a single fragment of this inter- 

 esting form. 



Occiti'i'rni-t'. Midwayan (Clayton limestone"): Mabelvnle, near Little Rock. 

 Arkansas (very rare). 



Holotype.Grt., No. (WT.ss. U.S.N.M. 



CONOPEUM DAMICORNIS, new species. 



Plate 3, figs. 3-S. 



Description. The zoarium is free, formed of two lamellae growing back to 

 back, irregularly bifurcated: the fronds are distorted. The zooecia are distinct, 

 irregular, polygonal, or elliptical: the mural rim is very thin, regular, projecting 

 but little, convex. The opesium has the same form as the zooecinm. The inter- 

 opesial cavities are polygonal and of a very great irregularity. 



. i7ifl=0.32 mm. . fLsO.'Bo mm 



Measurements. Opesia . /ooecia- , 



l/o=0.20 mm. 1/2=0.23 mm. 



Variation* inn] afffiuf /< .<;. This species has zooecia of a disconcerting irregu- 

 larity; it is absolutely impossible to discover among them a form the least constant. 

 The same holds true with the interopesial cavities which disappear following the 

 irregularities of the zoarinm. 



The structure of the zooecial walls is quite remarkable. In tangential sec- 

 tions (tig. i.)) these walls appear normal but in transversal thin sections, they are 

 thickened, crenulated on the inside, and composed of tissue not very dense (fig. 5). 

 In the median thin sections obtained by rubbing away bo<th sides of the fronds, a 

 structure may be noted identical with the zooecial walls; the olocystal elements 

 grouped around the mural rim appear to be chambered (fig. 7). Finally, a section 

 taken perpendicularly to the plane of the fronds (fig. 8) shows that the zoarium is 

 formed of two lamellae placed back to back and separable. 



The false chambering of the mural rim is not analogous to the formation of 

 dietellae in f'< riporoxilla ; we find in reality in every species chambered in this 

 way some large, scattered, unoriented olocystal elements (figs. 4. (>). 



The zoarium itself is quite, constant and characteristic; it often assumes, 

 although rather vaguely, among other shapes, the form of the IUH-HK of a deer, heucr 

 our specific name. As its zoarial dimension-- exceed two centimeters. \\e may con- 



