G32 NEW YORK STATE MUSEUM 



Dicliograptus logani Roemer & Freeh. Lethaea palaeozoica. 1897. 1:595, 



fig.162 

 Loganograptus logani Elles. Quar. Jour. 1898. 54:476 

 Loga'nograpt.us logani Ruedemann. N. Y. State Paleontol. An. Rep't. 1902. 



p.556, 570 

 Loganograptus logani Elles & Wood. Monogr. Brit. Grapt. ptl. Pal. Soc. 



for 1902, p.81, pl.ll, fig.la-g 



Description. Sicula, iiema aud primaiy disk not observed. Rliabdo- 

 some consisting of I'elatively long (aljoiit 2 . 1 nun) branches of the first 

 order (funicle), dividing dichotomously into four short branches of the second 

 order (about 1 A mm long). Twice repeated dicliotomous division in e(jually 

 short intervals leads normally to 16 branches of the fourth order. Sup- 

 pression of one or the other of the third dichotomies, or the appearance 



Fig. 46 Log'anograptus logani Hall. Enlargement of branch. Deep kill. x5.25 



of fifth dichotomies on some of the brandies results in variations in the 

 number of the branches, commonly ranging in our material between 13 and 

 25. All dichotomy takes place \\ithin 5 mm from the sicula, or mthin 

 the secondary disk. Branches of the last order ver}- long (7^ inches and 

 more according to Hall). Branches straight, nari'o^v, of unifoim width 

 (.8 mm wide). Thecae numbering 8 to 10 in 10mm, short, about three times 

 as long as wide, in contact for about half their length, inclined at 30°, their 

 outer margins very slightly concave, the apertural margins straight and 

 inclined to the axis of the branch under an angle of 150°. Large secondary 

 (central) disk pi-esent in larger specimens. 



Position and localities. In graptolite bed 2 (Tetragraptus zone) 

 occur fragments of branches which may belong to this species, but no 

 proximal parts Avei-e noticed. In graptolite bed 7 (zone of D i p 1 o - 

 g r a p t u s d e n t a t u s ) Avere found the specimens reproduced on plate 

 9, figures 3-6. Hall reports the species from the Point Levis beds; but 



