246 REPORT ON THE STATE CABINET. 



while a similar or identical form has been shown by Prof. M'Coy to 

 occur in Australia. We must, therefore, seek some other than an acci- 

 dental cause for the explanation of this uniform bifurcation of the stipes 

 of that species. In the meantime, it appears to me highly proper to 

 suggest its separation from Diplograptus. 



On farther comparison, we shall find that G. ramosiis is not quite alone 

 in its peculiar characters. In G. fiircatus there are a few cellules at the 

 base of a simple stipe below its bifurcation ; and in G. sextans, the lower 

 part of the stipe is simple, the division taking place above the first 

 cellule ; but in entire individuals the division is never from the initial 

 point, as we see it in G. hifidus and G. nitidiis. 



Now these first named species, as well as G. ramosus, have cellules of a 

 peculiar form; and looking still farther, we find a similar form of cellule 

 in G. forchhammen, Geinitz, and G. divcuicatus , Hall, two species which 

 are divided from the base, having a single range of cellules upon the 

 outer sides of the stipe. I believe it will be found, moreover, that all 

 the graptolites with cellules on the lower side of the stipes (in reference 

 to the initial point or radicle) have these parts of the same form as in 

 G. ramosus, and very unlike the G. pristis and allied species. Nor are the 

 cellules on the simple or divided portions of the same stipe, or on those 

 which are entirely divided, and upon the lower side, at all like the 

 cellules of G. priodon, G. geminus, G. murcMsom, or any of the allied forms 

 illustrated in this memoir to which the term Didymograptus has been 

 applied ; nor can they be properly united with them. The form of the 

 cellules is always sufficiently distinctive, even in fragments of the stipes ; 

 and this feature, together with the mode of development or growth, 

 seems to me sufficient to sustain a generic distinction. 



The Genus Retiolites is described by M. Barrande as having no cen- 

 tral solid axis, but with a single internal canal occupying the median 

 portion of the polyp. The prevailing form of the stipe is somewhat 

 concavo-convex, with the centre of the concave side prominent; the 

 entire surface is covered by a net- work of corneous substance, and 

 the cell-apertures are quadrangular. 



Prof Geinitz has given some further illustrations, showing more 

 distinctly a longitudinal axis on the convex side, to which are joined 

 the cell-partitions ; while he regards the common body as occupying the 

 prominent central portion of the concave face of the stipe, and showing 

 the cell-partitions terminating before reaching the centre, leaving a space 

 occupied by the width of the common body. This he represents as 



