BKYOZOA. 423 



NirHOLSONELLA (TMTLATA 

 PL XXXm, Fig. 6-6c. 



Zoarium very irregular, sometimes submassive, at other times 

 subramose, consisting of one or more superimposed layers, from 

 0.7 to 4 mm. in thickness, with the inner side generally covered 

 by an epithecal membrane or loosely attached to other bodies. 

 In one (a lobate mass having a tendency to become massive) 

 the central regions are solid in the sense that the tubes traverse 

 an ''axial region." Surface sometimes smooth, but generally 

 with low, rounded, rather regularly arranged monticules, two 

 mm. or a little more apart, measuring from center to center. On 

 these monticules the zooecia are scarcely larger than those in 

 the intermediate spaces, but they are separated by wider inter- 

 spaces. Zoopcial tubes slightly curved near the origin in each 

 layer, after which they proceed direct to the surface. In this 

 portion they are crossed by diaphragms from once to twice 

 their diameter apart. Apertures subcircular, the average dia- 

 meter 0.18 mm. ; when perfect with a faintly elevated and 

 minutely spinulose margin; about seven in two mm.; arrange- 

 ment moderately regular. Interspaces varying in width, usually 

 narrow, usually almost half as wide as the zooecia, occupied 

 by small, closely tabulated, angular mesopores, which, just be- 

 neath the aperture surface of each layer, are filled with a dense 

 deposit. The minute mural tubuli, best shown in this deposit, 

 are a less marked feature than in the more typical species. 



The habit of growth d'stinguish the species from both N. 

 ponderosa and -V. raupeli. The absence of stellate maculae dis- 

 tinguish specimens from an associated species of Constellaria, 

 that is closely allied to C. limit aris Ulr. 



Position and locality: Cincinnati group, Wilmington, Illinois; 

 very abundant. 



CONSTELLARIA Dana, 1848. 

 (Zoophytes, p. 537.) 



(For generic diagnosis see page 374.) 



The type of this genus is my C. tiorida* For many years it 

 was regarded as identical with Stellipora antheloidea Hall, and 



*Jour. Cin, Soc. Nat. Hist, Vol. V, p. 257. and VoL VI, p. 267. 



