14 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxx. 



in that it bridges tlie gap between the typical ramose s\)Qcies of Aniplexo- 

 pora and the massive forms, such as A. jiUosa or A. petasiforviis. 

 Occur' rence. — Eden shale, Cincinnati, Ohio, and vicinity. 



ARTHROPORA CINCINNATIENSIS (James). 

 Plate IV, fig. 7. 

 I*tilo(llctifa / cincinndticnsiK JaxMes, Paleontologist, No. 5, 1881, p. 39. 



This is one of the Cincinnatian species of Arthropora, a genus of 

 bifoliate bryozoa characterized bj?^ its regularly and frequentl}' jointed 

 zoaria. In its zooecial structure the species is ver^' similar to the 

 abundant A. .^Jiaffer! (Meek), but the respective zoarial peculiarities of 

 the two forms are so constant and evident as to justify their recogni- 

 tion as distinct species. James gave a fairly good description of his 

 species, a part of which is quoted below, and his diagnosis, together 

 with the iigure of the type presented on Plate IV, will prol)ably serve 

 for its ready identification. 



Oviqlnal description. — "Polyzoary * * *, consisting of sul)- 

 cylindrical, or cylindrical stems, giving off lateral branches from half 

 a line to one line apart at an angle, generall}' of about 45 degrees; 

 branches var\'ing in length from half a line to over one line; diameter 

 of stems about half a line. The pores vary from long oval to subcir- 

 cular in shape, and are arranged in alternating rows, three or four in 

 tiie space of half a line measuring their longer diameter (longitudi- 

 nally), and nearly twice that number transversely; separated, generally, 

 about their own diameter apart. * * * "■ 



Compared with Arthropora cleavelandi (James) with which A. cin- 

 clnnatiensh agrees most nearl}^ in growth, the latter may be distin- 

 guished by its smaller, nearly C3'lindrical and proportionally stouter 

 l)ranches, while in zooecial structure it differs in having decidedly 

 l)roader interzocecial spaces, causing the zooecial apertures to be much 

 smaller. .1. f<haiferl agrees better in the external appearance of its 

 zooecia, but differs decidedly in the greater size of its segments and in 

 their broader, relativelj^ shorter, more frequent, and compressed 

 lateral branches. 



Occurrence. — Not uncommon in the lowermost strata of the Mount 

 Hope member at Cincinnati, Ohio, and vicinity. 



ARTHROPORA CLEAVELANDI (James). 



Plate III, figs. 13-16; plate IV, fig.' 6. 



I^ilodicU/a cleavelandi Jamks, Paleontologist, No. 5, 1881, j). 38. 



Arthrojiora shafferi-cleavelundl Nickles and Basslek, Bull. U. 8. (tcoI. Surv., 



No. 173, 1900, p. 171. 

 PtUodictya f/ralianii J xyiEs, Paleontologist, No.^5, 1881, p. 39. 

 Ptilodictya duhia James, Paleontologist, No. 5, 1881, p. 40. 



Pfilodictya cleavelandi James, as shown by the type, is founded 

 upon segments of a rather well-marked species of Arthropora occur- 



