36 



BULLETIN 65, UNITED STATES NATIONAL MUSEUM. 



of branches is nbont 20 in 25 mm. of width. Dist;ill.v it rnn.ces from 14 to 

 17. The dissepiments are not very slender (reaching a width of 0.2 mm. 

 ad max.), straight or obliqne, sometimes two diverging from a conuuon i)oint 

 of origin on the branch. Length of meshes probably (when all the dissepi- 

 ments are i)reserved and visible) not much exceeding 2 nmi. Tlie dissepiments 

 are, in many places, obscure, but seem usually to be l..^)-2.0 mm. apart. Smallest 

 complete meshes about 1 mm, long. Branches obscurely striate. Thecje 

 invisible. 



Horizon and locality. — (Jlaciated chert l)eds, Niagara formation, Hamilton, 

 Ontario. 



This species is characterized especially by the very great thickness of its 

 branches, the general radiating aspect of the polypary, and the small number of' 

 branches transversely. 



I'lG. 45. DiCTTONEMA PERCRASSUS^ NEW SPECIES. RHABDOSOME WITH BA.SAL ATTACHMENT. 



Cotypes. — Collection of Walker Museum, University of Chicago. 

 Xo. 13511 ; Spencer collection. 



DICTYONEMA SPENCERI Gu.ley, new species. 



Plate 4, figure 1. 

 Doctor Gurley's description follows: 



Polypary circular or flabolliforni. consisting of heavy branches, mo.stly about 

 O.S nun. wide, some as narrow as ().»i nun., set about 17-20 in the proximal 

 ])ortion and usually about 20-22 in 2.^) mm. of width in the perijiheral portion 

 of the polypary, nearly straight, subparallel, with about 4 6r .^» bifurcations in 

 their course toward the perip.hery. Dissepiments usually slender, though an 

 occasional one reaches 0.5 mm., usually 1.5-2 mm. apart, and in many cases 

 a ;> nun. interval is seen without any trace of an intermediate dissepiment sub- 

 dividing this long mesh. But in other cases similar long meshes are seen, on 

 close inspection, to be subdivided by an intermediate dissepiment. Meshes sub- 

 quadrangular. 



Horizon and locality. — Five specimens from the Niagara chert, Hamilton, 

 Ontario. 



