GRAPTOLITES OF NEW YORK, PART 2 icr 



straight or slightly convex ventral and gently concave apertural margins; 

 they are apparently without apertural appendages. 



The specimen from our Clinton beds suggests in its habitus relation- 

 ship to D. gracile more than to any other form; in fact the differences 

 between D. scalariforme and D. gracile are so minimal as a com- 

 parison of their dimensions will show that a close relationship between the 

 two can not be doubted. Their main differences would seem to rest in 

 the smaller size of the rhabdosome and the closer arrangement of the dis- 

 sepiments in D. scalariforme. The la'.ter difference is more or less 

 invalidated by the fact that also in portions of D. gr a c i 1 e the dissepi- 

 ments approach each other sometimes to i mm. A third form which is 

 closely related to both of these species, according to its dimensions, is D , 

 venustum Lapworth [1881], which, moreover, is of the same period. 

 The present species stands nearest to the Scottish form but still differs in 

 the closer arrangement of the dissepiments. 



In our Clinton shale D. scalariforme is associated with Palaeo- 

 d i c t y o t a c 1 i n t o h e n s i s. 



Dictyonema retiforme Hall 



Plate 3, figure i 



Gorg.onia ? retiformis Hall. Geol. N. Y. 4th Dist. 1843. p. 115, fig. 1 

 Dictyonema retiforme Hall. Am. Jour. Sci. 185 1. 11:401 

 Dictyonema retiforme Hall. Pal. N. Y. 1852. 2: 174, pi. 4oF, fig. ia, ib 

 Dictyonema retiforme Hall. Can. Org. Rem. Dec. 2. 1865. p. 12, fig. 10 

 Dictyonema retiforme Hall. N. Y. State Cab. Nat. Hist. 20th Rep't. 1868. 



P.T78, fig. 11 

 Dictyonema retiforme Hall. Id. rev. ed. p. 2 10, fig. 11 

 Dictyonema retiformis Spencer. Can. Nat. 1878. 8:458 

 Dictyonema retiforme Spencer. Can. Nat. 1882. 10:165 

 Dictyonema retiforme Lesquereux. Geol. Sur. Intl. 13th Rep't. 1883. p. 30 

 Dictyonema retiforme Spencer. Acad. Sci. St Louis. Trans. 1884. 4:564,573, 



574, pi. 3. ng- 1, 2 

 Dictyonema retiforme Spencer. Mus. Univ. State Mo. Bui. 1884. 1: 14, 23, 24, 



pi. 3, fig. 1, 2 

 Dictyonema retiforme Miller. N. Am. Geol. Pal. 1889. p. 185, fig. 168 



