323 



BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



The zooecia have a compound operculum ; they are surmounted by a small, elon- 

 gated, constant zooeciule which is closed by a chitinous operculum. The female 

 zooecia bear a hyperstomial ovicell which is always closed by the operculum. 



Genotype. Trypostega (ScMzoporella) venusta Norman, 1864. 



Range. Jacksonian-Eecent. 



The organization of the female zooecia is very different from that of the 

 gonoecia of Hippotlwa. There is certainly a polypide; the larvae develop in an 

 ovicell embedded in the distal zooecia, but the ovicell is closed by the operculum. 

 It is probable that the larvae are different from those of the other genera. The 

 zooeciules (=suprazooecial chambers of Waters and dwarf zooecia of Levinsen) 

 are the organisms whose functions are unknown ; they are unprovided with polypide. 



E*150 



F75 



FIG. 94. Genus Tryiiostcya Levinsen, 1909. 



A-H. Trypostvga vcnusta Norman, 1864. A. A zooecium and two zooeciules, X 75. B. 

 Drawing showing three zooeciules and a larger one surrounding an ovicell, X 40. C. View from 

 the basal surface, X 40. Two ovicells are seen surrounded by zooeciules, which, like the ordinary 

 zooecia, are furnished with dietellae, X 40. D. Apertura, X 75. E, F. Opercula, X 150 and 75. 

 G. Apertura of zooeciule with operculum, X 200. H. Operculum of a zooeciule, X 200. (A-JI. 

 After Levinseu, ]909.) 



TRYPOSTEGA ELONGATA, new species. 



Plate 9, fig. 17. 



Description. The zoarium incrusts shells. The zooecia are distinct, elongated, 

 fusiform; the frontal is convex and perforated with numerous pores scattered and 

 disposed in quincunx. The apertura is formed of a large semicircular anter sepa- 

 rated by two cardelles from a small, somewhat convex poster. The ovicell is large, 

 salient, porous, elongated, carinated; it is hyperstomial and always closed by the 

 operculum. The zooeciules are elongated, fusiform ; their small orifice is elliptical. 



[LzOAO mm. 



T| f /< It W.VV/ 111111. _, . J^t& \J,^C\J 1I111J 



Measurements. Apertura 7 _ Zooecia , . - 



[?a=O.OSmm. lte=0.28mm. 



Affinities. This species differs from Trpostega venusta Norman, 1864, of the 

 Vicksburgian, in the greater length of its zooeciules (Zz=0.20 mm. instead of 

 0.10 mm.), and in its slightly smaller apertura. 



