700 ^■K^v York state jiuset'.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, 

 Avhich are provided with spines. 



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

 designated in this work as D. eadiiceiis 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 with the paracmic 

 mutation of D . caduceus, just cited. 



Didymograptus incertus sp. nov, 



Plate 15, figure 14 



Didymograptus sp. nov. Ruedemann. N. Y. State Paleontol. An. Eep't. 1902. 

 p.570 



Description. Primary disk and lyema not observed. Sicula apparently 

 rapidly tapering (longer than 1.5 mm). Branches reclined, first horizontally 



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

 110", their width in the proximal region about 

 1.2 mm, increasing to 1.9 mm and decreasing 

 again toward the distal ends. Thecae nuraber- 



Fig. 92 Didymograptus incertus '^ 



?^pr"oduced"J5'?u5.*flgyf4:''sho*w/f.tSS ing 8 to 9 iu 1 mm, inclined at an angle of 40°, 



ing of dorsal wall. Deep kill. x7 



three times as long as Avide, 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 iu 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 with the latter sjiecies, 

 D . caduceus mut. nanus, etc. 



RemavTcs. The sicula is preserved only fragmentarily and as an 

 impression. Its characters, as well as those of the first theca could therefoi'e 

 not be made out with sufficient accuracy. 



This form bears a superficial resemblance to D . caduceus and could 

 be taken for a representative of that species, in which the branches have l)e 'a 



