CAMBRO-SILURIAN MICRO-PALEONTOLOGY. 



41 



This genus is proposed, provisionally, for the reception of the pecu- 

 liar species next described. The 2:enus has very close affinities with 

 Dicranopora, and stands in precisely the same relation to that genus as 

 does Tceniopora, Nicholson, to Cystodictya, Ulrich. 



GONIOTRYPA BILATERALIS. (N. Sp.) 



Plate IX., fig. ... 



3 



1. Transverse section of a segment of Goniotrypa bilateralis, dividing it at a 

 point about midway of its length. 2. Transverse section of the lower end 

 of another segment in which, instead of non-celluliferous margins, there 

 is a row of zooecia on each side. 3. Tangential section of the upper half of 

 a segment, showing the form of the primitive portion of the zooecia, and 

 the somewhat pinnate arrangement of the parts with respect to the median 

 keel. 



Segments simple, about one millimetre wide and four to six mm. 

 long ; lower extremity obtusely pointed ; the upper truncate. Median 

 ridges strongly elevated, delicate and sharp in young examples, rounded 

 and somewhat granulo-striate in old specimens ; zooecia usually in four 

 rows on each face with two on each side of the median ridges. A third 

 row is occasionally developed along the sharp non-celluliferous margins. 

 Apertures ovate, those of the cells in the outer row usually much larger 

 than those of the inner. Frequently they are also separated by wider 

 interspaces. Normally, however, the number in a given space should 

 be nearly equal in the outer and inner rows. In the latter there are 

 fourteen in four mm. Interspaces obscurely striated. A faint peristome 

 generally surrounds the apertures of the zooecia. The strong central 

 ridges give the segments of this species such a distinct appearance 

 that they are not likely to be confounded with the associated species 

 of Dicranopora. 



Stony Mountain, Manitoba, Dr. R. W. ^\h, 1875, and Mr. T. C. 

 Weston, 1884. 



