432 PALEONTOLOGY OF ILLINOIS. 



Different examples show considerable variation in the number 

 of mesopores. The most marked features of this species are the 

 tenuity of the zoarium, the small size of the zocecia, the com- 

 paratively small number of mesopores, the large number and 

 extreme minuteness of the acanthopores, and the nearly equal 

 tabulation of zooecial tubes and mesopores. It prefers to attach 

 itself to the shells of Brachiopoda, though it is found adherent 

 to other organisms as well. 



Position and locality: Monroe Co., 111.; Chester, 111.; Pulaski 

 and Jackson Co., Ky.; and probably at all typical localities of 

 the Chester group. 



BATOSTOMELLA Ulrich, 1882. 



(Jour. Cin. Soc. Nat. Hist. Vol. V, p. 141 and 154). 

 (For generic diagnosis see page 375.) 



This genus attained its maximum and most typical develop- 

 ment during Carboniferous time. With perhaps three or four 

 exceptions, the Silurian and Devonian species present peculiari- 

 ties which, when once we have a good understanding of this 

 group of fossils, may necessitate their removal to other genera. 

 The two species next described belong to these doubtful forms, 

 but the four following them are typical members of the genus. 

 A small portion of a tangential section taken from an unusu- 

 ally well preserved example of B. gracilis is figured on plate 

 XXXV, fig. 2. It should be compared with the sections of B. 

 obliqua figured on plate XLVI. 



BATOSTOMELLA SIMULATRIX Ulrich. 



PI. XXXV, flg. 1-10. 



Zoarium dendroidal, throwing off cylindrical branches from 

 two to five mm. in diameter. Surface smooth, with clusters not 

 at all or but slightly elevated, in which the interspaces between 

 the cells are wider and mesopores more abundant than elsewhere. 

 Zooecial tubes a little irregular in their course in the axial por- 

 tion, quite oblique in the peripheral zone where their walls be- 

 come considerably thickened. Apertures of zooecia oval, owing 

 to the obliquity of the tubes, about 0.2 mm. in their longer 

 diameter and about eight in two mm. measuring longitudinally. 



