602 ' BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Osthimosia evexa Jullien, 1888. 



The known fossil species are; 



Osthimosia tub if era Canti, 1908, Patagonian of Argentina. 



Osthimosia, crassatina Canu, 1908, Patagonian of Argentina. 



Osthimosia parvicella Canu, 1908, Patagonian of Argentina. 



OSTHIMOSIA GLOMERATA Gabb and Horn, 1862. 



Plate 74, figs. 12-19. 



1862. Ccllepnraria glomcrata GABB and HORN, Monograph of the fossil Polyzoa of the Sec- 

 ondary and Tertiary formations of North America, Journal Academy of Natural 

 Sciences, Philadelphia, ser. 2, vol. 5, p. 134, pi. 19, fig. 15. 



Description. The zoarium is massive, globular, measuring as much as 2i 

 centimeters in diameter. The superficial zooecia are scattered, distinct, oval, quite 

 erect: the. frontal is smooth and surrounded by some large areolar pores: it bears 

 a median avicularium, with pivot, oval, with the point directed toward the base. 

 The apertura is orbicular and is provided with a very wide and rounded rimule. The 

 ovicell is large, smooth, transverse, recumbent; its orifice is very large and placed 

 above the apertura. The deep zocecia have a reduced frontal; the apertura and the 

 much enlarged aviculariiim are alone visible. The incomplete zooecia are quite 

 numerous and irregular. There are some interzooecial avicularia, small and with- 

 out pivot. 



\ha= 0.10 mm. 

 Measurements. Apertura , 7 . , 



17(7 = 0.10 mm. 



Variations. The superficial zooecia are generally quite erect (figs. 15, 17, 19), 

 but they are sometimes simply oblique (fig. 16). When the frontal avicularium is 

 broken we have then the aspect of the figure given by Gabb and Horn. In reality 

 hhe specimens of Schismopora globosa more often resemble this same figure. The 

 American authors cite their specimen as from Vicksburg. In this locality we have 

 only discovered the present species. We think, therefore, that our specimens really 

 represent the species described by Gabb and Horn, from a specimen which appears, 

 moreover, quite mediocre. 



The considerable enlargement of the frontal avicularium in the deep zooecia 

 is a useful phenomenon to note, for it occurs quite frequently. 



Specimens of this species are often covered with incomplete zooecia, which do 

 not allow serious determinations. Often, in fact, the zoarium of the Cellepores 

 dies suddenly without apparent reason before the complete formation of the zooecia. 

 In this species, as in all the massive or branched species, there are zooecia of all 

 sizes and forms. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (very 

 common). 



Middle Jacksonian: Wilmington, North Carolina (common) ; 3J miles south of 

 Perry, Georgia (rare). 



Vicksburgian (Byram marl) : Vicksburg, Mississippi (common). 



Plesiotypfs.Ca,t. No. 64209, U.S.N.M. 



