172 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



STAMENOCELLA INFERAVICULIFERA, new species. 



Fl.-ite 31. figs. 0-15. 



The zoarium is free with the two lamellae inseparable and growing back to 

 back. The zooecia are elongated, distinct, narrowed in back: the mural rim is 

 little salient, very thin, attenuate at its base. The opesium is elliptical or oval, 

 entire; the gymnocyst is flat, smooth. The marginal zooecia have no avicnlaria. 

 The ovicell is small, globular, fragile, placed on the gymnocyst of the distal 

 zooecia. closed by the opeivulum. The avicularium is situated on the inf< rir por- 

 tion of the gymnocyst in close contact with the mural rims of the proximal 

 zooecium. 



Measurements. Opesia 



0=0.30-0.36 mm. . fZs=0.70-O.T-t mm. 

 Zooecia 



/o=0.10-0.16 mm. la lte=:0.-24-030 mm. 



iix. This species is exceedingly variable and its study has required 

 considerable effort; moreover it appears at several distinct horizons in the Jack- 

 sonian and Yickburgian. The more perfect specimens shown in our figures are 

 extremely rare: the avicularium here assumes a peculiar form without axis or 

 pivot, which makes its nature doubtful. 



Figure 10 shows that on the same zoarium there may be extraordinary varia- 

 tions. Here the broken ovicell appears to be quite voluminous and to crowd the 

 avicularinm close to the opesium. In specimens from Monrotville, Alabama, the 

 proximal avicularium is smaller (fig. 10- In the course of weathering they become 

 smaller and smaller (fig. 11), divide in two. and even may be replaced by a few 

 pnnctations (fig. 13). 



The opesium is sometimes elliptical ami sometimes oval. The two forms ni vur 

 on the same specimen (fig. 7). 



The ovicell is quite variable in form and even in the same locality it is im- 

 possible to find it of a constant size and shape. 



Affinities. On certain rather well preserved specimens the avicularium is 

 identical with that of ^t,nn, inx-rll/i m< <Tm <-;<-<ti;fi /</ (figs. 7. 8). that is to say. it is 

 of simple form with neither axis nor pivot. In only a single instance (fig. 1:2) have 

 we observed a pivot which left no doubt as to the reality of this organ. 



Like the preceding species. ,S'. ///fV/v/i-/V////'/', ,-,/ is found principally in the Jack- 

 sonian although it is also common in the Vicksburgiau. 



Occi/i'i-i in'i . Middle Jacksonian (Castle Hayne limestone): Wilmington. 

 Xorth Carolina (very rare). 



Upper Jacksonian (Ocala limestone) : '.' mile- north of Ocala. Florida (rare) ; 

 Alachua. Florida (common). 



Vicksburgian (Marianua limestone): 1 mile north of Monroeville, Alabama 

 (common) : Salt Mountain, 5 miles south of Jackson. Alabama (rare) : west bank 

 of Conecuh River. 1 mile below mouth of Sepulga River. K-rambia County. Ala- 

 bama (rare) ; Murder Creek, cast of Custlduiry. Conecuh County. Alabama (rare). 



Vicksburgian (Red Bluff clay) : One-fourth mile west of Woodward. Wayne 

 County. Missi ippi (rare). 



i otypes.Cat. No. <'.:W1 --?>?M:>. T.S.X.M. 



