NO. 1442. JAMES TYPES OF BRYOZOA—BASSLER. 17 



that an immature zone is present as in nearly all Paleozoic bryozoa, 

 but this region is so short that it will not be noticed unless the section 

 is made in the manner indicated above. Numerous acanthopores and 

 closely tabulated mesopores are developed in the mature region, while 

 each zooecium generally shows a single large cystiphragm occupying 

 the bend from the immature to the mature region. Rarel}^ a second 

 and even a third may be developed above the first. 



Aspidopora calyenla is the only described species of the genus 

 occurring in the particular strata in which it is found, while from 

 associated bryozoa the discoid zoarium with numerous mesopores and 

 acanthopores and the zocecial tubes with "large cystiphragms will serve 

 as a ready means of separation. 



Occuirence. — Not unconuuon in the Bromley shale of the Trenton, 

 exposed along the Ohio River bank opposite Cincinnati, Ohio. 



ASPIDOPORA ECCENTRICA (James). 



Plate ?I, tigs. S-12; plate V, figs. 7, 8. 



Moiificulipora {Heterolrypa?) eccentrk-a James, Paleontologist, No. 6, 1882, p. 48; 



No. 7, pi. I, figs. 6, 6o. 

 MoiiticiUipora eccentrica J ames and James, Jour. Cincinnati Soc. Nat. Hist., X, 



1888, p. 167, pi. II, figs. 2a-c. — J. F. James, Jour. Cincinnati Soc. Nat. Hist., 



XVI, 1894, p. 185. 

 Aspidopora eccentricaVhRicn, Geol. and Nat. Hist. Surv., Minnesota, Final Rept., 



Ill, Pt. 1, 1893, p. 255. 



Zoarium a small, free, subcircular expansion averaging 4 mm, in 

 diameter and 1 mm. or less in thickness. Occasionall}' several of these 

 disks may be found in contact and forming a zoarium as in A. areolata 

 Ulrich. Celluliferous face smooth, slightly convex, and 'showing that 

 the zoarium is composed of a single macula surrounded by zoa?cia of 

 the normal size. Under stirface flat or concave and lined with an epithe- 

 cal membrane whose wrinkles or lines of growth are arranged about a 

 point nearer the margin than the center of the base. Zocecial aper- 

 tures rounded or ovate, the average diameter of the ordinary zooecium 

 0.3 mm. with 6 in 2 mm. while the largest zooecia of the maculae attain 

 a diameter half again as great. Mesopores rather numerous, 6 usually 

 surrounding a zooecium and occupying the interspaces left by the zocecia 

 where their walls fail to touch. Acanthopores few and small and sel- 

 dom detected either in sections or on the specimens. 



The internal characters of this form differ but little from other 

 species of the genus. The large, elongate but few cystiphragms and 

 the absence of diaphragms characterize the zocecial tubes while the 

 mesopores are, as usual in this genus, closely tabulated. 



This neat little species can readily be recognized by its small subcir- 

 cular zoarium and the eccentric wrinkles of the epithecated side. The 

 species seems to he restricted to the middle division of the Eden shale 

 in the Cincinnati area. Washings from certain shale beds will often 

 Proc. N. M. vol. XXX— 06 2 



