ORDOVICIAN FAUNAS. 141 
3mm. Those forming the clusters vary in size, generally, from 0.25 
to 0.88 mm. Acanthopores wanting. 
“Internal Characters—These, as shown in over one hundred thin 
sections, are very constant in all the essential parts. In tangential 
sections the form of the zocecial tubes varies from perfectly circular 
to polygonal, their walls in most cases being very thin, and the cavity 
of each intersected by the crescentic edges of one or more cysti- 
phragms. The opening left by the cystiphragms is generally lateral 
and of bi-convex shape; occasionally it is subcentrally situated and 
oval, but more commonly two or more cystiphragms combine to give 
it a subtriangular form. An abnormality is sometimes met with in 
the confluence of two zocecia. The zocecia are in contact with each 
other only in part, perhaps only at limited points, the imterspaces left 
between them being occupied by small mesopores. These vary some- 
what in number, and more so in size, but are always decidedly angular. 
At intervals they are collected into substellate macule of greater or 
less extent, and in the immediate vicinity of these the zocecia are 
of appreciably larger size than elsewhere. No evidence whatever of 
acanthopores has been detected. 
“In vertical sections the cystiphragms form continuous series on 
one or both sides of the tubes, according as they extend all around 
the circumference or embrace only a portion of the same, while an 
equal number of straight diaphragms crosses the remaining portion 
of the tube.”—Ulrich. The tabulation of the tubes is quite uniform, 
the cystiphragms averaging sixteen or seventeen in 2 mm. In the 
mesopores the diaphragms are simple, and average about eighteen in 
1 mm.° 
Remarks.—This species of bryozoan is the most common one in 
the Trenton limestone of New Jersey. As it usually occurs, it is 
firmly imbedded in the limestone, so that only the cross-sections of 
the specimens can be observed. Only rarely is a complete colony 
weathered free from the matrix. Thin sections of the New Jersey 
specimens show them to be identical with the typical form of the 
species as described from Kentucky, Tennessee and Minnesota. The 
variety orientalis, said to come from New York and Canada, has not 
been detected among the New Jersey specimens. 
