ISOTRYPA. 181 



corresponding to the true dissepiments, the thickened summits are connected by 

 strong processes, giving to the superstructure an appearance very much like that 

 of the reverse face of the frond. Zooecia in two ranges." 



Though I have referred the following species to this genus as being that to 

 which it seems most nearly to approach, it hardly seems to me that it can come 

 within its limits, and I should be more inclined to refer it to a new genus with the 

 following definition : — " Zoaria infundibuliform. Branches connected with dis- 

 sepiments. Keel at first thin, then gradually expanding, and bearing on its 

 summit strong bars which contain double rows of supplementary cells and are 

 united by occasional scalse. Zooecia in two intermittent ranges. Intervals filled 

 with vesicular tissue." Suggested name, " Amorphotrypa." 



1. Isotryfa? Gregorii, ii. sp. PI. XX, figs. 1 — 2 e. 



Description. — Zoarium deeply conical or funicular, rising from a thick massive 

 base of attachment, and consisting of a double framework filled with coarse vesicular 

 tissue. Inner or zocecial framework formed of straight, narrow, convex branches, 

 smooth and non-poriferous on the inward face, and swelling at the dissepiments, 

 which are straight and level or continuous, so that the short oblong fenestrules 

 do not alternate, but are arranged in level rows. Branches bearing along their 

 outward side lengthways a series of lofty monticules, which appear to be placed at 

 the insertion of the dissepiments, and which contain two large cells divided by a 

 thin central partition or knife-edge, which rises together with the contracted walls 

 for about a length equal to the cells through the vesicular tissue to the outer 

 framework, which consists of broad longitudinal beams, bluntly triangular 

 externally, corresponding to the branches, and apparently containing on their 

 inward side small cells or triangular pustules at the rate of four to a dissepiment ; 

 these beams being perhaps joined to each other by intermediate dissepiments or 

 dense tissue. 



Size. — A small specimen measures 20 mm. in height, and 10 mm. in diameter 

 across the top. 



Locality. — Lummaton. There are three specimens in my Collection, one of 

 which has been used for making sections. 



Remarks. — This is a decidedly puzzling fossil. After a very careful examination 

 Dr. Gregory and myself came to the conclusion that of the genera given by Ulrich 

 it most probably agrees with Isotrypa. At the same time there are several points 

 which render it very doubtful whether it can properly be referred to that genus, 

 and a subsequent examination very much inclines me to the opinion that, unless 

 it can be referred to Fenestrapora, a new genus must be founded for it, as suggested 

 above (Amorphotrypa). 



