Description of a JSfeio Genus and some New Species 125 



few in number, probably never more than three, and generally only 

 one or two in each tube. From eight to ten, or even twelve tubes oc- 

 cupy the space of one line. 



Longitudinal sections show the tubes to be transversely divided by 

 diaphragms, placed at corresponding levels in contiguous tubes. The 

 diaphragms are about two thirds of a tube diameter apart. The tube 

 walls in the lower portions of the tubes are very thin ; they become 

 thicker as the surface is approached. A peculiar feature is the peri- 

 odic swelling of the walls at heights coincident with the tabulae. In 

 the minute tubuli the diaphragms are more closely set than in the lar- 

 ger tubes. 



It would be quite impossible to confound this species with any other 

 form, since it differs more or less in nearl}" all particulars from those 

 previously described. 



Formation and locality' : the species occurs in the upper beds of the 

 Cincinnati Group, at Jacksonburg, Butler Co., Ohio. 



Collector: E. O. Ulrich. 



Atactopora septosa, n. sp. (Plate XII., figs. 7, 7a, 76, 7c.) 



[Eity.—Septosus, having partitions or septa.] 



A ramose species, growing from an expanded base, b}^ which it is at- 

 tached to foreign bodies. Branches bearing considerable resemblance 

 to those of Chcetetes {MonticuUpora) pulchelhis ov Jletcheri. Surface 

 exhibiting low, broad and rounded tuberosities; which are placed at 

 distances apart of about one line, and carr^^ groups of larger tubes 

 than those of the ordinary size. Tubes small polygonal, quite regular- 

 ly arranged, without any minute interstitial cells; walls thin; about 

 eight of the tubes, of average size, occupy the space of one line; about 

 six of the tubes of larger size, occupy the same space. Pseudo-septa 

 well developed, more easily detected in slightly worn specimens than in 

 those perfectly preserved; from one to five in each tube. 



In longitudinal sections the tubes are seen to be nearly vertical in 

 the middle of the branch ; here the}' have very thin walls, and are crossed 

 by excessively thin and remote tabulte; they then bend abruptly out- 

 ward, and as the surface is approached the tabulae are more closely set, 

 and the walls become stouter; here also the pseudo-septa make their 

 appearance, as is demonstrated by the darker lines which extend 

 parallel with, and between, the true walls of the tube. The diaphragms 

 are so thin that they can easily be overlooked. 



In tangential sections the pseudo-septa are very conspicuous, and 



