616 



BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



oriented in radial fibers around the lyrula. These fibers are visible even on the 

 internal walls (fig. 6). When the section is deeper (fig. 13) the zooecia are sep- 

 arated by the habitual black line; the olocystal elements of the walls are grouped 

 in more or less diffused links. The transversal fracture of the zoarium (fig. 9) 

 indicates a concentric lamellar structure, the use of which is yet to be demonstrated. 





n 



' . 



... 

 '* '*' '.* 



. ,r 



pic .... 



Bx20 



Cx20 



FIG. 186. Genus Acanthionella Canu and Bassler, 1917. 



A-F. Acanthionella tyjnca Gabb and Horn, 1862. A. View of the bifoliate zoarium (, b), 

 the incrusting base, natural size (c), the two lamellae (a), and the surface (e), enlarged, show- 

 ing the lyrula and the pores. (After Gabb and Horn, 1862.) B. Schematic drawing of a vertical 

 section, X 20. ap, apertura ; ol, olocyst ; ov, ovicell ; pic, peristomice ; z, zooecium. C. Photo- 

 graph of the surface, X 20. The lyrula and the olocyst frontal with avicularia are shown. 

 D. Interior of the zooecia, X 20, illustrating occurrence of lyrula. E. Another interior, X 20, 

 with the ovicell showing in three of the zooecia (at the top). F. Tangential thin section through 

 the frontal of the zooecia, X 25. The olocystal structure of the frontal is shown. Cretaceous 

 (Vincentown), Vincentown, New Jersey. 



Affinities. This species differs from Acanthionella typica Gabb and Horn, 

 1862, in its frontal gibbosities and in the presence of a porous area on the ovicell. 



Occurrence.- Claibornian (Gosport ?and) : Claiborne. Alabama (common) ; 

 1 mile south of Eockville, Clarke County, Alabama (very common) ; Gopher Hill, 

 Tombigbee Biver, Alabama (rare). 



Lower Jacksonian (Moodys marl) : Jacksoi. Mississippi (( imon). 



Cotypes. Cat. No. 63861, U.S.N.M. 



