354 CRETACEOUS PALEONTOLOGY. 



more or less tortuous. Zooecia as seen on the growing margin 

 of the zoarium, b-roadly suboval in form, but in the mature por- 

 tion becoming more or less rhomboidal with the outer wall 

 slightly concave, and in very old zoaria their borders not differ- 

 entiated; they are arranged more or less irregularly or in quin- 

 cunx, and have a length of about 0.3 mm. Zocecial apertures 

 rounded anteriorly, the proximial margin straight, and when 

 perfect with a small tooth-like process extending forward from 

 the median line, usually about 0.125 mm. in width. Avicularia 

 from three to five, about each zooecium, one, usually a little 

 larger than the others, situated just in advance of the zooecial 

 aperture, two others, one on either side, nearly opposite the 

 posterior margin of the aperture, and frequently a second pair on 

 opposite sides of the posterior portion of the zocecium ; these 

 avicularia are subcircular, and are usually bordered by an ele- 

 vated rim-like border. Ovicells rare or absent altogether. 



Formation and locaUty.^Vmcentawn limesand, Vincentown 

 (154), Timber Creek and near M^llica Hill (Gabb and Horn). 



Geographic distrihiUion — ^New Jersey. 



Mucronella aspera Ulrich. 



Plate XXVI. , Figs. 14-15. 



1901. Mucrortglla aspera Ulrich, Md. Geol. Surv., Eocene, p. 

 221, pi. 60, figs. 17-18. 



Description. — "Zoarium incrusting, consisting of one or more 

 layers ; surface, under a low power of magnification, presenting 

 a decidedly rough aspect. Zooecia varying from ovate-hexa- 

 gonal, to sub-rhomboidal, indistinct externally, arranged more 

 or less irregularly, though the rows are more regular than they 

 appear at first sight; about six in 2 mm. Apertures rounded 

 or subquadrate, 0.13 mm. in diameter, rendered oblique by the 

 elevation of the more or less strongly swollen posterior margin 

 and the depression of the anterior part. The central portion of 

 the raised lip forms a "mucro" of greater or less thickness and 

 prominence, the same hiding a minute central tooth beneath it, 

 and forming with the rest of the thickened portion of the lip, 



