216 BULLETIN 17, UNITED STATES NATIONAL, MUSEUM. 



oped at the end of a fold of the wall which in the most mature con- 

 dition extends far into the zocecial cavity. 



The internal structure as exhibited in tangential sections has been 

 discussed above and the septal folds of Nicholson shown to be the 

 greatly infolded, zocecial wall bearing an acanthopore. Vertical sec- 

 tions are especially interesting for the reason that they exhibit the 

 diagnostic generic character — the zonal thickening of the walls 

 accompanied by an accelerated development of acanthopores. The 

 characters of such a section, with two successive immature and 

 mature zones, are shown in figure 118 a. Nicholson's vertical section 



Fig. 118.— Stigmatella fookdh. a, vertical section, X20, passing through two layers of zooecia; 



&, TANGENTLA.L SECTION, X20, WITH THE ZOCECIA SHADED; C, PORTION OF THE SAME SECTION, X35, "WITH 

 FEW ACANTHOPORES; d, ANOTHER PORTION, X35, SHOWING AN EXTREME DEVELOPMENT OF THE IN- 

 FOLDED ZOCECIAL wall; e, several ZOCECIA OF A TANGENTLiL SECTION, X50, WITH SMALL ACANTHOPORES 

 PLAINLT DEVELOPED AT THE ENDS OF THE INFOLDED WALLS. KtTCKERS SHALE (02), BARON TOLL'S 

 ESTATE, ESTHONIA. 



includes only the mature region of a single zone, but the tabulation 

 of both sets of tubes is the same as in the original of figure 117 a. 



Without careful comparison, the zocecial characters of the present 

 form seem almost identical with those of Stigmatella injiecta, but the 

 zooecia of the latter are almost twice the diameter of the former. 

 Internally the two species are quite distinct, especially in the tabula- 

 tion. No American species with which either might be compared is 

 known. 



Occurrence. — Rare in the Kuckers shale (C2), Baron Toll's estate, 

 near Jewe, Esthonia. 



Plesiotype.—Csit. No. 57298, U.S.N.M. 



Section of figured specimen in the collections of the British Museum. 



