218 THE PALEONTOLOGY OF MINNESOTA. 



[MontlcuUpora wetherbyl. 



MONTICULIPOEA. WETHERBYI Ulrick. 



PLATE XV, FIGS. 7 and 8. 



MonticuKpora wetherbyi UleicH, 1882, Jour. Cin. Soc. Nat Hist., vol. v, p. 239, pi. X, flgs. 4-46; 1889, 



Contri. to the Micro-Paleon. of the Cambro-Silurian Rocks of Caoada, 

 pt. 11, p. 30. 



Zoarium attached to foreign objects, forming thin crusts or small depressed- 

 conical masses. Surface gently monticulose, sometimes nearly even. Zooecia 

 polygonal, with very thin walls, the diameter of those of the ordinary size about 

 0.25 mm. Clusters of larger cells attaining a diameter of from 0.3 to 0.38 mm. 

 occupy the summits and slopes of the monticules, or in. the smooth forms are 

 scattered over the surface at intervals of about 2.5 mm., measuring from center 

 to center. A few small cells (? mesopores) may be detected, especially at the center 

 of the monticules, but they are always an inconspicuous feature and being of various 

 sizes are probably to be regarded as merely young zooecia. Acanthopores rather 

 large and numerous in tKe original Kentucky types of the species, small and few in 

 the northwestern form. 



In longitudinal sections the zooecial tubes have thin walls with the granulose 

 structure characteristic of the genus. The transverse partitions, occurring at inter- 

 vals of a tube-diameter or more in the lower half of the tubes and little more than 

 a third of that distance apart near the surface, seem really to be all of the nature of 

 cystiphragms, though frequently appearing in the sections as straight diaphragms. 

 In transverse sections the tubes are angular and thin-vpalled, with strong acantho- 

 pores — one at most of the angles — in the Kentucky specimens, and much smaller 

 and fewer ones in the Minnesota and Manitoba form of the species. The cystoid 

 nature of the diaphragms is generally recognizable in these sections, but the cresentic 

 line, which is the unfailing mark of these structures, may not be detected except in 

 only a few of the zocecia. 



Formation and locality.— USLie in the Birdseye limestone of central Kentucky. A single example was 

 found in the lower limestone at Minneapolis. The species also occurs at St. Andrews, Manitoba. 



Mus. Reg. No. 5967. 



