700 NEW YORK STATE MUSET'M 



to show as closely approaching branches as the Mt Moreno form. The latter 

 differs from all these still further by the looser arrangement of the thecae, 

 ^vhich are provided with spines. 



While this form does not possess the general gerontic aspect of the form 

 designated in this work as D . c a d ii c e u s mut. nanus, it appears as an 

 extreme development of D. caduceus by the divergence and slenderness 

 of the branches and has the spinous apertures in common Avith the paracmic 

 mutation of D . caduceus, just cited. 



Didymograptus incertus sp, nov. 



Plate 15, figure 11 



Didymograptus sp. nov. Ruederaann. N. Y. State Paleontol. An. Rep't. 1902. 

 p.570 



Description. Primary disk and nema not observed. Sicula apparently 



rapidly tapering (longer than 1.5 mm). Branches reclined, fii'st horizontally 



(about 2 mm), then diverging at an angle of 



110°, their width in the proximal region al)out 



1.2 mm, increasing to 1.9 mm and decreasing 



^. „„ „., , . affain toward the distal ends, Thecae number- 



Fig. 92 Didymograptus incertus ^ 



r^prXced^of pU5*fl!/f"1hois'?ha" lug 8 to 9 iu 10 mm, inclined at an angle of 40°, 



ing of dorsal wall. Deep kill. x7 _ _ 



three times as long as wide, in contact for one 

 half to two thirds of their length. Outer margin slightly convex, apertural 

 margin concave, mucronate. 



Position and locality. A single specimen was found in graptolite bed 7, 

 horizon of D i p 1 o g r a p t u s d e n t a t u s ; associated ^vita the latter species, 

 D . caduceus mut. nanus, etc. 



Remarhs. The sicula is preserved only fragmentarily and as an 

 impression. Its characters, as well as those of the first theca could therefore 

 not be made out with sufficient accuracy. 



This form bears a superficial resemblance to D . cad u c e u s and could 

 be taken for a representative of that species, in which the branches have be ':i 



