BRYOZOA. 435 



walled. Zooecial apertures separated by thick interspaces, oval, 

 variable in size, the average long; diameter being 0.1 mm., six 

 or seven in two mm., measuring lengthwise. Mesopores small, 

 moderately abundant, circular or broadly oval. Diaphragms 

 often wanting in the zooecial tubes, never numerous; generally 

 lacking in the mesopores. Acanthopores very numerous, arranged 

 in a circular band about each zocecium. 



The peculiarities of tabulation, the thick walls, and vast num- 

 ber of acanthopores, causing the spinulose aspect of the surface, 

 are the most noticeable features of this species. 



Position and locality: Chester group. Abundant at Sloan's 

 Valley, Pulaski Co., and other localities in Kentucky; worn 

 specimens from Chester, 111., are referred doubtfully to this 

 species. 



BATOSTOMELLA ABRUPTA Ulrich. 



PI. LXXV, fig. 2-2e. 



Zoarium dendroidal, from two to three mm. in diameter. Sur- 

 face smooth, hirsute, with clusters of somewhat larger cells. 

 Zooecial tubes inclining gently outwards from their origin, rather 

 oblique even in the cortical region, causing the apertures to 

 have a somewhat oval shape. Apertures about eight in two 

 mm. When in a good state of preservation the apertures are 

 surrounded by a sloping space. The thick interspaces are oc- 

 cupied by one or two rows of closely arranged small acantho- 

 pores. When in two series, they are separated by a groove in 

 which an occasional mesopore of small size may be detected. 

 Walls of zooedal tubes abruptly thickened in the unusually nar- 

 row cortical region. An occasional diaphragm developed in the 

 zooecial tubes. 



The somewhat more robust growth, very narrow cortical 

 region, the larger cells, and the abruptly thickened walls, are 

 the principal points which distinguish this species from B. spinu- 

 losa, found in the same beds. 



Position and locality: Chester group, Sloans Yalley, Pulaski 

 Co., Ky. Probably occurs at Chester and other localities in 

 Illinois. 



