NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



277 



Genotype. Macropora central!* MacGillivrny. 1895. 



Range. Jacksonian-Eecent . 



Levinsen classed this genus in the Microporidae, but the absence of the opesiules 

 and parietal muscles oblige us to place it under the Pseudostega. Perhaps it will 

 be convenient to create a family of Macroporidae : but we arr absolutely without any 

 knowledge of its anatomical features. 



MACROPOBA AQUIAE, new species. 



Pliite 1. figs. 20. 21. 



Description. The zoarium incrusts small shells. The zooecia are hexagonal, 

 somewhat elongated, distinct, separated by a more or less salient thread; the crypto-' 

 cyst is very slightly concave and quite finely porous. The aperture is semilunar. 

 transverse ; its proximal border 

 is straight with two small lateral 

 characteristic indentations; the 

 vestibular arch is very small. 

 There are two pairs of lateral 

 dietellae. 



Measurements. j Aa 0.04 mm. 

 Aperture lZa=0.08mm. 



. [7,3=0.40 mm. 

 Zooecia , . ... 



l?.3=0.20mm. 



Variations and affinities. 



The micrometric measurements * c , M 

 are quite variable. The ances- 



trilla is a zooecium identical with FlG - 78 - Genus Macropora MacGillivray, 1895. 



the Others. The thread separat- A ~ D - ^"^opora centralis MacGillivray, 1895. A. Three 



ing the zooecia often becomes zooecia 'X 23.; ra, vestibular arch. B. The aperture of a 



, rr,, .., , 



quite attenuated. The vestibular 



special lorm of zooecium (avicularium?1, X 40. C An 

 O p er culum with its surrounding x 40. I) A dietella ) 



arch is visible only when greatly 40. CA-D after Levinsen, 1909.) 

 magnified. 



The frontal occasionally bears some perforations which appear to be opesiule*. 



This small species is extremely fragile. It is not rare in the Aquia forma- 

 tion. to which it appears to be restricted. 



Occurrence. Lowest Eocene (Bryozoan bed at base of Aquia formation): 

 Upper Marlboro, Maryland (not uncommon'). 



Holotype.Cat. No. 63780. F.S.N.M. 



MACROPORA MULTILAMELLOSA, new species. 

 Plsite 41. figs. 1-3. 



Description. The zoarium is multilamellar and incrusts algae or creeps over 

 the sand ; the zooecia of the upper and external lamella only are living. The ex- 

 ternal zooecia are hexagonal, elongated, distinct, separated by a prominent thread ; 



