588 NEW YORK STATE MUSEUM 



The general habit of the types of this genus, due notably to the 

 plumose arrangement of the branches on a principal axis, is, as Hall has 

 first pointed out, extremely suggestive of recent hydrozoans, such as 

 Plumularia and Aglaophenia, but this similarity is evidently only the result 

 of convergence. Also Freeh [189 7 J adduces these genera for comparison. 

 The latter genus has one iiematocalyx or neraatophore-beaiing cell 

 in front and one on either side of each hydrotheca. It is with these 

 defensive and prehensile individuals that Freeh would compare those con- 

 sidered as gonangia by Wiman. 



The group of forms comprised under the generic term Ptilograptus, is 

 a very small one ; for the exploitation of the rich homotaxial faunas of 

 other countries has increased but very little the number of species described 

 by Hall, namely by a form only doubtfully referable to this genus, described 

 by Hopkinson from Wales. We add here a third species to the two known 

 from the Quebec shales of Point Levis. 



Ptilogfraptus plumosus Hall 



Plate 4, tljfiire U, 15 



Ptilograptus plumosus Hall. Canadian Organic Remains, decade 2, 1865. 



p.l40, pl.21, fig.l, 2?3, 4 

 Ptilograptus plumosus Billings. Geol. Sur. of Can. Palaeozoic Fossils. 1865. 



1: 366,375 

 Ptilograptus plumosus Ami. Geol. Sur. of Can. Report 1889. ser. 2, v. 3, 



pt2,p.ll7k 

 Ptilograptus plumosus Hall. N. Y. State Cab. Nat. Hist. 20th An. Rep't. 



pl.4, fig.16 

 Ptilograptus plumosus Gurley. Jour. Geol. 1896. 4: 300 

 Ptilograptus plumosus F. Roemer & Freeh. Lethaea palaeozoica, Bdl. 



1897. p.579, fig.151 

 Ptilograptus plumosus Ruedemann. N. Y. State Paleontol. An. Rep't. 



1902. p.570 



Description. Rhabdosome consisting of an irregularly branching princi- 

 pal stem and branches provided with alternately arranged closely set branch- 



