CAMBRO-SILURIAN MICRO-PAL.IIONTOLOGY. 29 



in from two to seven irregularly alternating ranges, and, where best 

 presei'ved, are provided with strongly elevated apertures. 



A careful comparison between this species and P. auloporoides will 

 most probably prove that the former is only a variety of the latter. 

 I can see no difference between them except that in the number of 

 ranges of the zooecia. Though I have not given this group of bryozoa 

 the study it demands, I have, nevertheless, examined enough material 

 to learn that when the zo(Ecia form more than one range, their 

 number is too variable to be accorded specific importance. 



Stony Mountain, Manitoba, where the only specimen seen was col- 

 lected by Mr. T. C. Weston in 1884. 



MONTICULIPORA PARASITICA, Yar. PLANA. (N. YaR.) 



Plate YIII., figs. 3-3d 



The typical form of this species-"^ may be described briefly as follows : 

 Zoarium parasitic, forming thin crusts upon shells and Streptelasma, 

 frequently consisting of several layers, each about one millimetre thick. 

 Surface studded with small, abruptly elevated, conical monticules, 

 arranged in decussating series, two to five mm. apart. Apices of monti- 

 cules generallj' appearing solid, but, when in a good state of preserva- 

 tion, are occupied by a variable number (three to ten) of minute shallow 

 cells. Zooecia polygonal, thin-walled, with thirteen or fourteen of 

 those of the ordinary size in three mm. ; those surrounding the monti- 

 cules are larger, some being three-tenths of a millimetre in diameter. 

 Internally the zooecial tubes exhibit complete series of cystiphragms, 

 between two and three occurring in a space equal to the diameter of 

 a tube. Walls minutely granular or punctate, rather thin, and usually 

 enclosing a small lucid spot (acanthopore ?) at the angles of junction. 



The Manitoba variety differs from the typical examples of the species 

 in being without monticules. On the other hand, the clusters of large 

 cells are comparatively more conspicuous, some of them being at least 

 four-tenths of a millimetre in diameter. In the minute internal struc- 

 ture they agree very closely. The j^eculiar structure of the zooecial 

 wa\h of tvne species of MonticuUpora is shown very well in fig. Sc. 

 The new variety is so far known only from a specimen collected by 

 Mr. T. C. Weston at Stony Mountain in 1884. The original examples 

 of M. parasitica were collected from the upper beds of the Hudson 

 Eiver or Cincinnati group at Oxford, Ohio. The species is now known 



*Monticulipora parasitica, Ulrich. 1883. Journ. Cin. Soc. Nat. Hist., vol. 5, p. 238, pi. 10, 

 flgs. 3-3a. 



