1 62 NEW YORK STATE MUSEUM 



contains a fragment from the Rochester shale at Lockport. This form is 

 easily distinguished from both its associated congeners, D. retiforme 

 and D. gracile by its more irregularly bent branches and the oblique 

 direction of the dissepiments. By these characters it seems to lead directly 

 to Calyptograptus subretiformis Spencer with which it is also 

 associated. 



The thecae have not been seen in full profile in any of our specimens. 



On account of the interest which this form has gained as one of the 

 more common graptolites of the Rochester shale, we insert here the figure 

 of D . t e n e 1 1 u m Spencer, referred by Gurley to D. polymorph u m , 

 since it represents a complete specimen, and camera enlargements of 

 Gurley's type [fig. 72] and of material from Middleport, N. Y. 



Dictyonema subretiforme (Spencer) 



Plate 2, figures i, i 



Calyptograptus subretiformis Spencer. Can. Nat. 1878. 8: 458, 460 



Calyptograptus subretiformis Spencer. Can. Nat. 1882. 10: 165 



Calyptograptu ¥ s subretiformis Spencer. Acad. Sci. St Louis. Trans. 1884. 



4: 5 6 4, 57 8 . 579; pl- 4, fig- 1 (not figure 2) 

 Calyptograptus subretiformis Spencer. Mus. Univ. State Mo. Bui. 1884. 



1 :24, 28, 29; pl. 4, fig. 1 (not figure 2) 



Calyptograptus subretiformis Gurley. Jour. Geol. 18. 4: 93, 308 



Several good specimens of this species, one a complete colony, were 

 obtained in the Rochester shale at Middleport, N. Y. Spencer's original 

 description of the species as it occurs in the Niagara limestone at Hamilton, 

 Ontario, is : 



Frond circular, but cyathiform in its growing state. There are numer- 

 ous bifurcating branches, which in the fossil condition imperfectly unite or 

 overlie each other producing a kind of fine network with irregular subrhom- 

 boidal I ellipsoidal, 1884] interstices. In texture it is corneous, having the 

 branches marked with striations of a subrhomboidal form. 



In this species the branches are much finer (but little more than 

 J/so inch in width, 0.35-0. 75 mm, 1884) than in C. cy ath if ormis, with 

 more numerous and irregular bifurcations, producing a netted appearance. 

 The original matter is often replaced by pyrites. The fronds arc not gen- 

 erally more than 2 inches in diameter. Only a few specimens have been 

 found, and these show some varietal differences. 



