226 REPORT ON THE STATE CABINET. 



approach more and more to the cylindrical form, as in Rastrites. As 

 examples of cellules contracted towards the aperture, we have Graptoli- 

 tJius priodon, Barrande, and G. ciintonensis, Hall (Plate i, figs. 1, 2 and 3). 



M. Barrande has remarked that from the circumstance of the partial 

 or complete isolation of the successive alveoles of the same series, we 

 may easily conceive that the walls of contact in contiguous cellules should 

 be double. This fact he has ascertained from decomposing specimens of 

 G. priodon ; and we have the same evidence in some of our species. In 

 the cellules of the ordinary mode of development, each one is an inde- 

 pendent part of the organization, and is provided with its individual 

 body and cell- walls, as if each cellule were isolated. Whenever two of 

 these are in contact, the cell- walls coalesce as far as the contact con- 

 tinues ; but when becoming free, the cellule assumes its normal condition. 

 In some specimens of Phyllograptus we find this evidence of double 

 walls in the cell-partitions. 



In G.putillus, illustrated on Plate ii, figs. 10, 11 and 12, the cell-walls, 

 although contiguous to and adjoining the walls of the body (and not free), 

 do not coalesce, but are readily separable without fracturing their sub- 

 stance, and the same is true of G. ciintonensis. 



There are cellules, however, where the production of the calycle by 

 budding from the common body is not so obvious. These forms are like 

 G. bicomis and G. anttennarius , where the orifice is a simple transversely- 

 oval aperture in the side of the stipe ; and in the flattened specimen, it 

 appears like a rectangular or slightly oblique semi-oval notch in the 

 margin. Its true form is perceived only when the cavities of the polyp 

 have been filled with mineral matter, or when the stipes are flattened 

 vertically against the apertures : they then give the form which has 

 been described as G. scalaris. This form of cellule is shown on Plate ii, 

 figs. 1 and 2, which are enlarged from a specimen retaining nearly its 

 original proportions. Just within the limits of the cellules, and extend- 

 ing the entire length of the stipe, there is a longitudinal depressed line; 

 and along this line, and running thence almost rectangularly to the outer 

 limits of the stipe just above the aperture, the cell-partitions join the 

 exterior test, and project in an extended border or flange. 



In specimens stripped of the test, where the interior has been filled 

 with stony matter, the cell-partitions present the appearance shown in 

 Plate ii, fig. 3 ; while there is a large central space apparently occupied 

 by the common body, but without the appearance of a central axis on 

 the exterior surface. When the surface is ground down to a plane inter- 



