64 LOWER PENINSULA. 



cning- of the tube walls, but in other specimens the alteration 

 reaches a still hi^jhcr dec'ree. 



DENDROPORA ELEGANTULA, Billings. 

 Synon., Trachypora Elegantula, Billings. 



Small ramified stems, from two to five millimeters in diameter. 

 Orifices longitudinally oval, oblique, effuse above, the remainder 

 of the circumference being edged by a projecting rim ; they are 

 arranged in four longitudinal rows on the stems, but often the 

 regularity of the rows is disturbed by interposition of single orifices 

 in the intervals between. Interstitial spaces broad, decorated 

 with flexuose and interlacing rugae, covered by delicate granules^ 

 and rendered minutely porous by a superficial punctiform and fis- 

 sure-like perforation of the wall substance. On the surface the 

 walls of the single tubes are quite undefined, while in the centre of 

 the stems the walls are much thinner, and are well defined from 

 one another, exhibiting lateral connecting pores and transverse 

 diaphragms. The bottom of the conically dilating orifices is gener- 

 ally formed of a stout obliquely situated diaphragm. Diameter of 

 orifices in transverse direction one millimeter ; in longitudinal one 

 and a half millimeter ; internal tube cavity much narrower. 



Occurs rarely in the Hamilton group of Thunder Bay, near 

 Broadwell's mills, where it is associated with several other species 

 of Dendropora. The specimens represented on Plate XXIII. , Fig. 

 2, are from the Hamilton group of Widder, C. W., the locality from 

 which Billings described his original specimens. 



DENDROPORA ALTERNANS. 



Stems of about four millimeters in diameter, with remote oval 

 orifices in quincuncial position, forming about five loose, alternating, 

 longitudinal rows in the circumference of a stem. Diameter of orifices 

 lengthwise from one and a half to two millimeters, and one milli- 

 meter in transverse direction. Margins raised into an obtuse cir- 

 cumvallation. Surface minutely punctate by acutely pointed gran- 

 ules, but not ornamented with longitudinal rugae. Occurs associated 



