BRYOZOA. 283 
Callopora pulchella.] 
The small size of the branches and bushy habit of growth distinguish the species 
from all the other known Minnesota species of the genus. Externally its zoaria are 
exceedingly like those of an undescribed form occurring in the Cincinnati quarries 
associated with C. dalei Ed. and H. 
Formation and locality.—Very abundant in the upper third of the Trenton shales, rare in the Galena 
shales, at St. Paul and Cannon Falls, Minnesota. 
Mus. Reg. No. 8112. 
CALLOPORA PULCHELLA, %. Sp. 
PLATE XXII, FIGS, 1-12, 
Zoarium dendroid, branches averaging 5 mm. in diameter, tapering slightly, the 
oldest parts sometimes attaining a diameter of 7 mm., the young extremities only 3 
or4mm. The branches divide dichotomously at average intervals of 12 mm., and 
never, so far as observed, inosculate. Surface exhibiting small conical monticules, 
2.0 to 2.5 mm. apart, their summits generally with small aggregations of mesopores. 
As shown in the figures, the hight of the monticules varies in different examples, and 
in*some they are to be described as rounded rather than conical. Zocecial apertures 
small, subcircular, enclosed by rather thick, ridge-shaped walls, regularly arranged, 
subequal, thirteen or fourteen in 3mm. Mesopores very small and, though numer- 
ous, often difficult to distinguish externally with an ordinary pocket lens. This 
difficulty is greatest in old examples in which they are partially filled by calcareous 
deposits. 
Internal characters: Vertical sections show that in the axial region the prox- 
imal end of the tubes is crossed by from two to four diaphragms, beyond which these 
structures are absent till we reach the middle of the comparatively wide peripheral 
region when each zocecial tube is again intersected by one or two. Mesopores are 
abundant and closely tabulated. In tangential sections the zocecia are subcircular, 
their walls somewhat ring-like and in contact with each other in only a limited 
degree, the interspaces being occupied by more or less numerous mesopores varying 
considerably in size and shape. Just beneath the surface of a fully matured example | 
the walls are thickened by internal deposit, the mesopores small and approximately 
of uniform size. At deeper levels the walls are thinner and the mesopores larger and 
more irregular in shape and size. In transverse sections the axial region is made 
up of decidedly angular tubes of which those of the larger set are also comparatively 
small, while those of the minor set are less regularly distributed than usual. 
This form is to be compared with the C. dalet Edwards and Haime, of the Cin- 
cinnati group, from which it differs chiefly in having fewer diaphragms and slightly 
