244 REPORT ON THE STATE CABINET. 



species {G. piitillus, from the Hudson-river formation in Iowa), which 

 has come under my observation in some well-preserved fragments, we 

 have so far a modification of the general arrangement of the cellules 

 that the apex of one l^arely reaches the base of the next succeding. 

 The stipe is a strong elliptical tube with a flattened central solid axis, 

 the line of which is marked on the exterior by a longitudinal undulating 

 groove (Plate ii, fig. 10). The surface is strongly striated transversely, 

 and the sides studded with tubular cellules, which are alternately 

 arranged. These cellules are sub-oval, flattened on the side adjoining 

 the body of the graptolite, curving on the exterior free portion, and 

 obliquely flattened at the base just above the aperture of the cellule 

 next below, as shown in the profile view (Plate ii, fig. 11). The exterior 

 test of the common body is swollen in oblique undulations in the direc- 

 tion of the base of the cellules, or where the individual buds take their 

 origin ; and the axis is curved towards the opposite side as shown in fig. 10. 



The transverse diameter of the stipe is about two-thirds as great as 

 the longer diameter. The celluliferous face of the stipe shows broad 

 elliptical depressions ; the lower side, for little more than half the height, 

 being the sub-oval cell-aperture ; while the upper part is the semi-oval 

 flattened area at the base of the next succeeding cellule, as shown in 

 (Plate ii, fig. 11). In this case the cellules are shown to be separate 

 and distinct tubes, closely pressed against the lateral walls of the stipe 

 on one side, and communicating with the common body by a slightly 

 narrowed passage, as shown in Plate ii, fig. 12, which represents a longi- 

 tudinal section of the body. In a transverse direction, the base of the 

 cellule is wider than the aperture (Plate iii, fig. 11). 



Specimens of this character, on becoming flattened, would present a 

 form where the cellules, though inclined against the common body, 

 would not overlap each other, and where the margin of the cellule is 

 directed backward instead of forward. Were these cellules to be pro- 

 longed, they would overlap the next in advance, presenting in this con- 

 dition but a slight modification of the usual forms of Diplograptus. 

 These deviations from typical forms are so slight as to offer no sufficient 

 ground for generic separation. 



There are, however, a few examples, where the stipe is marked by a 

 range of cellules upon each side of the central axis, which appear to be 

 properly separated from Diplograptus, on account of the form and struc- 

 ture of the cellules. These are apparently quite unlike those of G. pristis, 

 and others of that sub-genus. The Gmptolitlms hiconiis, and two or three 



