Description of a JSFew Genus and some New Species. 123 



are no groups of larger sized tubes, the monticules are conical, and 

 regularh' arranged. 



Formation and locality: all the specimens examined wei'e found in 

 the Cincinnati Group at Hamilton, Butler Co., Ohio. It is not a com- 

 mon fossil. 



Collectors: H. E. Dickhaut, E. O. Ulrich. 



Atactopora mundula, n. sp. (Plate XII., figs. 4, 4a.) 



[Ety. — J/uadulus, neat.] 



Bryozoary parasitically attached to the fronds of Choetetes (3fonti- 

 culipora) mamniulatiis ; grows in thin expansions of less than one inch 

 in diameter; thickness less than one half a line. Surface at regular in- 

 tervals raised into rather prominent tubercles, placed a little more than 

 one line apart (measuring from center to center), and arranged in diag- 

 onally-intersecting lines; surface of monticules occupied b}^ calices of 

 the ordinary size. Tubes poh'gonal, with thick walls, the interstitial 

 spaces occupied by numerous minute tubuli, that are best observed in 

 worn specimens. Tube mouths small, of very irregular shape, but of 

 nearh^ equal size, ten to twelve in the space of one line; pseudo-septa 

 well developed, varying from two to five in each tube. No spines nor 

 granules appear to have been developed; the superior ends of the sep- 

 tal ridges, however, sometimes are a little prominent, and thus simu- 

 late spines. 



Although closel}^ related to A. ortoni, Nicholson, this species has 

 certain characters by which it can be easily distinguished from that 

 form. In that species the walls of the tubes are rather thin and gran- 

 ulated, and there are no true intertubular cells, while in A. mundula, 

 the walls are thick, not granulated, and are provided with numerous in- 

 terstitial cells. The monticules are larger and not compact as they are 

 in A. ortoni. Worn examples of A. multigranosa bear some resem- 

 blance to this species, but the thinner walls, non-tubular intercellular 

 spaces, irregular growth and disposition of the maculae in that species, 

 will serve to distinguish them. 



Formation and locality: near the tops of the hills about Cincinnati, O. 



Collector: E. O. Ulrich. 



Atactopora tenella, n. sp. (Plate XII., figs. 5, 5a.) 



[Eiy .—Tetiella , delicate.] 



Biyozoary, like that of the foregoing species, parasitic, forming ex- 

 ceedingly thin, irregularly outlined expansions, of an inch or more in 



