368 Systematic Paleoktology 



ChILOTRYPA MICROrORA n. sp. 



Plate XLI, Figs. 9-12 



Description. — Zoarium rising into irregularly inflated, hollow branches, 

 expanding in the specimens seen, from 5 mm. to about 10 mm. before 

 bifurcation takes place; thickness of zoarial wall usually but little more 

 than 1 mm. Surface even, but presenting well defined, though small, 

 subsolid maculae, about which the zooecia are arranged in a radial manner ; 

 zocecial apertures very small, broadly elliptical, a little the highest on the 

 lower or lunarial side, causing them to appear as opening somewhat 

 obliquely; diameter of a single zooecium .10 to .12 mm., with about 8 in 2 

 mm. Interzooecial space one and a half to three times the width of a 

 zooecium, smooth and slightly concave. 



The deposit of sclerenchyma in the interzooecial spaces at and near the 

 surface, characteristic of the genus, is shown in thin sections. Vertical 

 sections through the center of a branch show the central tube to be wide 

 and irregularly contracting and expanding; the zooecia are seen to arise 

 from the epitheca, to run nearly parallel with it in the short immature 

 region and then turn abruptly outward to form the mature region. Dia- 

 phragms thin, few, two or three being developed in the mature region 

 only. Interzooecial spaces are filled with large vesicles which become 

 smaller and more numerous toward the surface, and at the surface itself is 

 seen the dense calcareous deposit. In tangential sections, at a level below 

 the deposit, the large, angular vesicles are shown forming but a single 

 row between the small elliptical or nearly circular zooecia. The lunarium 

 is not sharply defined, being distinguished chiefly by a slight thickening 

 of about half the circumference of each zooecium. One to three lucid 

 spots may usually be distinguished in the lunarium. 



The extraordinarily small size of the zooecia, coupled with unusually 

 large interstitial vesicles, characterize this species so sharply that compari- 

 sons are unnecessary. FistuIiporeUa minima, an associated form, re- 

 sembles this species somewhat in the size of the zooecia, but its different 

 habit of growth, granulose surface, distinct lunarium, and unlike internal 

 structure, make up an assemblage of characters so obviously dissimilar that 

 confusion between them is scarcely possible. 



