158 



BULLETI]Sr 7*7, UNITED STATES NATIONAL. MUSEUM. 



peristome around the sides and front margin, 0.08 mm. wide and 0.16 

 mm. in length. 



Fragments of this characteristic American Richmond species are 

 not uncommon in the collections from the Lyckholm limestone. The 

 delicacy of their branches, as well as the characters noted above, will 

 distinguish these from all associated bryozoans. 



Occurrence. — Girardeau limestone division of the Richmond group, 

 Alexander County, Illinois; Lyckholm limestone (Fl), Kertel, on 

 the island of Dago, Esthonia (Cat. No. 57252, U.S.N.M.). 



British Museum, one specimen from the Lyckholm limestone, Ker- 

 tel, island of Dago. 



NEMATOPORA LINEATA (Billings). 



Text fig. 79. 



Eelopora Uneata Billings, Cat, Sil. Foss Anticosti, 1866, p. 36. 



Nematopora Uneata Ulrich, Geol. Surv. Illinois, vol. 8, 1890, p. 646, pi. 29, figs. 



7-7e. 



Certain thin layers in the lower part of the Anticosti group on the 

 island of Anticosti, Gulf of St. Lawrence, are crowded with fragments 

 of a rather robust species of Nematopora described by Billings as Eelo- 

 pora Uneata. Ulrich has figured the essential external and internal 

 features of the species, referring it to his genus Nematopora. Speci- 

 ^ mens indistinguish- 



able from this Ne- 

 matopora are con- 

 d "^ 7*^ i '■ \M' ^ tained in the solid 



limestone of the 

 Borkholm forma- 

 tion. 



Compared with 

 other species of the 

 genus, the branches 

 of Nematopora Une- 

 ata are quite stout, 

 averaging a milli- 

 meter in diameter. 

 They are distinctly 

 hexagonal in trans- 

 verse section on ac- 

 count of the zooecial arrangement in six rows separated by longitu- 

 dinal ridges. The lineate appearance given the branch by these 

 ridges is increased by the development of a second ridge, usually con- 

 necting the zooecia. Measuring lengthwise, three and one-half zooecia 

 occur in 2 mm. 



Fig. 79.— Nematopora lineata. a, fragment, natural size; b, sur- 

 face OF SAME, X18; C, VERTICAL SECTION, X18; d AND C, TWO TRANS- 

 VERSE SECTIONS, X18; /, PORTION OF €, X50, SHOWING MINUTE AXLVL 

 CANALS AND WALL STRUCTURE. RICHMOND DIVISION OF ANTICOSTI 

 GROUP, ISLAND OF ANTICOSTI. (AFTER UlRICH.) 



