NORTH AMERICAN EARLY TERTIARY BRYOZOA. 233 



Genus AECHMELLA Canu and Bassler, 19f7. 



1917. AirliiiicUa CANU and BASSLEK, Synopsis of American Early Tertiary Cueilostome 

 Hryozoa, Bulletin 96, United States National Museum, p. 29. 



The polypidian convexity is little prominent. The opesiules are round, lateral 

 indentations. The opesium is often contracted by two lateral teeth at the level of 

 the opercular hinge. The ovicell is endozooecial. The avicularium is interzooecial, 

 smaller>than a zooecium, lozenge shaped, with the form of the head of a lance. 



Genotype.- Aeclimflla filimarr/o Canu and Bassler. 1917. 



Range. Cenomanian-Miocene. 



The genus Aechmella is in effect Gargantua with avicularia. It may also be 

 regarded as Floridina with avicularia replacing the onychocellaria. 



The species of the genus are : 



Aechmella (Cellepora) michaudiana D'Orbigny, 1850. 



Aechmella (Cellepora) hippocrepis Hagenow, 1851. 



Aechmella (Cellepora) roemeri Lonsdale. 



Aechmella (Cellepora) xiphia D'Orbigny, 1852. 



Aechmella (Cellepora) xanthe D'Orbigny, 1852. 



Aechmella (Cellepora) urania D'Orbigny, 1852. 



Aechmella (M embranipora) depressa MacGillivray. 1904. 



Aechmella (MembrQnipora) concinna MacGillivray, 1904. 



Aechmella (Membranipora) ambigua MacGillivray, 1904. 



It is probable that one part of Homalostega Marsson, 1887. may be classed in 

 this genus. 



AECHMELLA CRASSIMARGO, new species. 



Plate 37, figs. 1, 2. 



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

 elongated, joined by their mural rims; the mural rim is incomplete, projecting in 

 front, thick on the borders, distinct from the cryptocyst. The cryptocyst is shallow, 

 a little convex, and smooth ; the opesium is almost transverse, trifoliate, contracted 

 by two lateral teeth at the level of the opercular pivot; the polypidian convexity 

 is scarcely visible; the opesiular indentations are shallow and symmetrical. The 

 ovicell is endozooecial. The ancestrula is a small zooecium of the same form as the 

 normal ones. The avicularium ir interzooecial, smaller than the zooecia, lozenge- 

 shape, with a small distal canalicule and an elliptical oppsium. 



[7(0=0.08-0.10 mm. 

 Measurements. Opesium , ,, ., 



Uo~0. 12-0.14 mm. 



Ls ^ 32 _ OAO mm _ 

 ? , =0 . 24 _ . 30mm _ 



Zooecium 

 (including the opesmlar 



indentations) 



Affinities. We have observed only a small number of specimens which were 

 thought for a while to represent forms of ancestrula r zooecia of Aechmella fiH- 

 marc/o. Nevertheless, we now believe it necessary to consider this a distinct 



