BRYOZOA. 605 



0.5 to 0.7 or 0.8 mm. between the bifurcations. Dissepiments 

 rounded, depressed, expanding but little at their ends, about 

 two-thirds the width of the branches. Fenestrules oblong sub- 

 quadrangular or oval, their width varying from one-fourth to 

 one-half the length; about six in 1 cm. longitudinally. Carina 

 strong, rounded, dilating into prominent elongated tubercles at 

 intervals of 1 mm. Zooecia in four ranges, two on each side of 

 the carina. Apertures sometimes alternating, usually opposite, 

 those of the lower ranges opening obliquely or directly into 

 the fenestrules and often obscured by those of the upper rows. 

 When the matrix completely fills the fenestrules the lower rows 

 are not seen and the specimens might be mistaken for Fenes- 

 telki. There are six or seven apertures in each row to a fenes- 

 trule. one of them opposite each dissepiment. The apertures 

 are of medium size, surrounded by a thin peristome, their dia- 

 meter or a little more apart, with eighteen in 5 mm. 



On the reverse the branches are narrowly rounded, smooth or 

 finely granulose, have sloping sides, are straight or slightly zig- 

 ;ind appear much thicker than on the opposite side. The 

 dissepiments are straight, nearly as strong as the branches, 

 and but little if at all depressed. The fenestrules vary consider- 

 ably in width, but are always wider than the branches, and 

 once and a half or twice as wide as on the obverse face. In 

 form they vary from quadrangular to hexagonal. 



The above .describes the typical form as it is found in the St. 

 Louis limestone at Alton, Illinois, and St. Louis. Mo. Prout's 

 figures are faulty in having the dissepiments as high as the 

 branches when they are really depressed. In the Warsaw beds 

 i variety that appears to agree in every respect except- 

 ing that its branches are invariably somewhat thinner. A more 

 distinct variety or species differs as follows: 



var. COMPACTA n. var. 



PI. LIX, Fig. 1. 



The branches are as a rule a little thinner and closer together 

 there being 11.5 to 12.5 in 1 cm.: the nodes on the keel incon- 

 spicuous or wanting, but large nodes often occur on the reverse. 

 The dissepiments depressed, rather strong and rounded, the 



