DENDROID GRAPTOLITES OP HAMILTON, ONTARIO. 31 



always heavy (0.4, 0.0, 0.8 mm.), though as seen they are sometimes slemler, 

 usually transverse, sometimes oblique. Meshes coarse, rectangular, about 3 

 mm. or more in length, though occasionally one is seen as short as 1.5-2.5 mm. 

 Apparently the length may reach 5 or even 6 mm., but in one mesh of this 

 character two intermediate dissepiments can be made out on close observation. 

 So that the superficial aspect of the fossil is not to be implicitly trusted. 



Careful comparison with the three species {ivebsteri, retiforme, pcrcrassns) 

 to which this form comes nearest, shows it to be distinct from all ; from the 

 last two it may be known by the absence of the rapid radiation of the polypary. 



fl orison and locality. — Two specimens in National ]\Iiiseiim, both 

 from the Niagara dolomite, Hamilton, Ontario. 

 Holotype and paratype.—C-at. No. 55299, U.S.N.M. 



DICTYONEMA EXPANSUM Spencer. 



Dictyonema cxpansum Spencer. Trans. Acad. Sci. St. Louis, IV, 1884, pp. 

 564, 575, 576, pi. 2, fig. 1 ; Bull. Mus. Univ. State Missouri, I, 1884, pp. 

 14, 25, 26, pi. 2, fig. 1.— GuRLEY, Journ. Geol., IV, 1890, pp. 96, 308. 



Spencer's original description is as follows: 



Frond flabelliform, composed of slender, expanding, and bifurcating branches, 

 diffusely arranged, and united laterally by slender filaments (often wanting) ; 

 branches irregularly striated ; texture corneous. 



This species is clearly related to D. gracUc in the relative size of the branches, 

 but these are much more diffusely and irregularly arranged, with greater inter- 

 spaces, which are from two to four times the width of the branches. The 

 transverse filaments occur less frequently than in D. gracile. Fragments of this 

 species are not always easily distinguishable from D. gracile, although the 

 branches are looser and more si)reading. The type specimen is 8 cm. high and 

 about 10 broad, rising from a united base of five or six stipes. 



Formution and locality. — Niagara limestones at Hamilton, Ontario. 



Doctor Giirley describes a specimen of this species as follows : 



Theiv is in ,ill the Hamilton collections but one specimen which I could by 

 any possibility refer to Spencer's c.rpanstmn. It may be described as follows: 



Polypary 120 mm. high and 235 nun. broad; flabelliformly compressed, semi- 

 circular in outline, consisting proximately of eight parallel branches, and higher 

 up of numerous branches, which are approximately straight (or with long, 

 sweeping curves) and subparallel ; the extreme lateral ones perpendicular to 

 the median line of the pclypary, nearly straight, the whole curvature occurring 

 proximally in a short turn. Width of branches pretty uniformly 0.8 mm., one 

 being occasionally seen 1 mm. wide. Distally the specimen is so worn that 

 it is hard to say whether the full width is maintained to the i)eriphery or not, 

 but a few unworn branches there measure 0.8 mm. The branches are every- 

 where set about 17 in 25 mm. of width. Concerning the number of dissepi- 

 ments, nothing can be said, the specimen being too much worn. No thecas are 

 visible. 



Horizon and locality. — One specimen in Spencer's collection, labeled Dic- 

 tyonema retiforme, from the Niagara dolomite, Hamilton, Ontario. 



I can not say that I feel entire confidence in the identification, but T think 

 this is Spencer's species. As above remarked, it is the only one in the collec- 

 tions which could be expansum, and it agrees as well with Spencer's descrip- 



