170 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



oblique, thin distally, much enlarged and transformed into a cryptocyst proximally; 

 the gymnocyst is little convex and smooth. The opesium is anterior, elliptical, 

 entire. The avicularium occupies the surface of the gymnocyst; it is large, salient, 

 and terminated like the beak of a duel', with spatnlate mandible. 



Ao =0.35-0.40 mm. . \Ls=0.85-1.00 mm. 



Opesia to= ' al7 mm \Jz = O.U mm. 



Affinities. The figured specimen is the only one that has been found and it 

 unfortunately has no ovicell. The large avicularium is not constant, although 

 many of the zooecia are unprovided with them; their presence is therefore not 

 necessary to each zooecium. We think that the function of the avicularia, like 

 that of the vibracula, is rather zoarial. 



Among the species of the same genus this is the only one in which the crypto- 

 cyst is much developed : its relationships with the genus Amphiblestrum are there- 

 fore close; but in the latter there is no gymnocyst and the avicularia are lodged 

 in the interzooecial angles. 



The disposition of the zooecia is also much less regular than in the other 

 species of Stcnni>nof<:11fi. It differs from Stamenocella grandipora in its small 

 opesial length (0.35 instead of 0.50). its cryptocyst, and chiefly in its large avicu- 

 larium in the shape of a duck's beak. 



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

 rare). 



,t. Xo. 63937, U.S.N.M. 



STAMENOCELLA PYRIFORME. new species. 



Plate 30, figs. 13-16. 



Description. The zoarium is bilamellar with narrow fronds; the two lamellae 

 are back to back and separable. The zooecia are very long, narrow, distinct, sep- 

 arated by a salient thread. The opesium is narrow, pyriform, the point toward 

 the bottom, bordered by a collar. The cryptocyst is smooth, developed laterally 

 and inferiorly to the opesium. The ovicell is globular, salient, embedded in the 

 cryptocyst of the distal zooecium; its orifice can not be closed by the operculum. 

 The avicularium is small, salient, elliptical, provided with a pivot or two lateral 

 denticles. 



. [Ao=0.32-0.35 mm. . [Ls=OM-O.QO mm. 



Measurenn nts. Opesia , Zooecia , 



1/0=0.10-0.15 mm. I7s=0.15-0.20 mm. ' 



Variation*. The lateral zooecia have an elliptical and nonpyriform oposinm 

 (figs. 13, 14). On the very wide fronds there are many rows of these different 

 zooecia. The avicularia of the lateral zooecia are much more prominent and ap- 

 pear claw-shaped ifii:-. 13. 14). 



When it is properly illuminated, the peculiar orifice of the ovicell is quite 

 visible. It is large, placed above the opesium. and the opercular valve can never 

 close it. 



