BRYOZOA. 413 



in tangential sections, situated in the walls of the zocecia, from 

 three to five surrounding each zooecium; also at some of the 

 angles between the mesopores. 

 Position and locality: Cincinnati group, Wilmington, 111. 



HETEROTRYPA Nicholson, 1879. 



(Pal. Tab. Corals p. 291.) 

 (For generic diagnosis see page 371.) 



As defined by Dr. Nicholson this genus included very diverse 

 material, the only characters common to the assemblage being 

 the possession of two sets of cells (i. e. zooecia and mesopores). In 

 the "Am. Pal. Bry." I have shown that only one of the seven- 

 teen species which he refers to the genus is congeneric with the type 

 species. H. froiidosa d'Orb., (H. mamniulata Xich., non d'Orb). 

 The remaining fifteen species are distributed among the genera 

 Callopora, Homotrypa, Amplexopora (?), Monotrypella, Bato- 

 stoina and Batostonwlla. The amended definition of the genus 

 as then proposed by me is now somewhat modified by the eli- 

 mination of H. vaupeli, which I now refer to Nicholsonella. 

 The restricted group is closely allied to Dekayia Ed. & H., and 

 comprises at least nine species, all of them from the Cincinnati 

 group. Three of these remain undescribed. 



HETEROTRYPA PROLIFICA Ulrich. 



PI. xxxvn, fig. i-id. 



Zoarium frondescent, or subramose with much flattened 

 branches, varying in thickness from four to twelve mm., and at 

 times attaining a height of ten cm. Low rounded tuberosities 

 arranged in irregularly interesecting lines and composed of cells 

 a little larger than the average, commonly surrounding a clus- 

 ter of mesopores. serve to break up the monotony of an other- 

 wise smooth surface. Zocecial tubes curving in the axial region, 

 direct throughout the peripheral region, where their walls be- 

 come considerably thickened. Zooecia apertures sub-polygonal, 

 about eight in two mm., and 0.15 to 0.18 mm. in diameter. 

 Interspaces occupied by calcareous matter: where very wide by 

 a few mesopores with illy defined walls. Most of the mesopores 

 are found in the clusters. A few diaphragms in the axial re- 



