GRAPTOHTES OF NEW YORK, PART 1 615 



(about .4 inm wide in the dorsal aspect and .6 mm in the lateral aspect), 

 straight in the central parts and slightly flexuous in the distal region, 

 branching dichotomously in irregular intervals. Branches of six orders 

 observed ; the bifurcation of the first branches takes place under right 

 angles, those of succeeding orders under angles of 50°-70°, the angles of 

 bifurcation decreasing distally. The thecae number 11-13 in 10 mm; they 

 are inclined at a constant angle of 25°, and are in contact for a little 

 more than one third of their length ; their outer walls are straight or 

 slightly concave, the apertural margin gently convex and nearly vertical 

 on the axis. 



Position and localities. Common in the Upper Cambric slates at 

 Schaghticoke N. Y. It occurs undoubtedly at other places in the slate 

 belt, in Rensselaer and Washington counties, in association with 

 Dictyonema flabelliforme. It is, for instance, very common in 

 Upper Cambric slates from Hillsdale near Granville, Washington co. 

 Emmons obtained his types from the Taconic slates of Kensselaer county, 

 N. Y. Matthew records the species as occurring in bands of 

 division 3 of the St John group, where it is also associated with 

 D. flabelliforme. 



Development. This species has furnished a complete series of growth 

 stages. These begin with (1) the sicula [pl.2, fig.l, 2], which is suspended 

 by a rather short nema from a thin cliitinous disk ; (2) the sicula produces 

 at about one third of its final length the first theca [fig.3], which grows 

 appressed to the sicula nearly as far as the latter's aperture and thence turns 

 to the left [fig.4, 5, 6] ; (3) from the first theca originates at about one 

 fourth of its length [fig.4:] the second theca, which also grows along the 

 sicula to the point of departure of the first theca and then turns to the right 

 side. The " f unicle " of other dichograptids, which is composed of these 

 two thecae, is, hence, here not noticeable in a horizontally spread out 

 colony. (4) Both primary thecae produce by budding in rapid succession 

 two apparently dichotomous branchings [fig.6] close to the aperture of the 

 sicula; thus gi\ing origin to the crucifonu division in the center of the 



