388 NEW YORK STATE MUSEUM 



Field Club, Lapworth stated his belief that this form is allied to Glosso- 

 graptus but that the evidence at hand is not yet sufficient to justify its 

 removal to that trenus. 



From Gurley's notes I learn that he has followed this suggestion of 

 Lapworth and used the finely preserved material from the type locality of 

 the species for an investigation of this important taxonomic problem, 

 arriving at the following conclusion : 



Specimens from Lake St John show that the structure of the species 

 has been entirely misapprehended, and that its affinities are retioloid rather 

 than diplograpticl. The thecal openings are bounded by continuous fibers 

 (mouth ledge, etc.) and the lateral faces show (partly in one specimen, 

 partly in another) the remains of a periderm, and the fibers when seen, cor- 

 respond fully to the parietal ledges of Holm. The last show virgular con- 

 nections in places and form on the lateral faces a network whose interstices 

 are filled with a black carbonaceous matter, similar to the periderm found 

 in Retiograptus ge i n i t z i a n u s. Indeed the structure is so like the 

 latter genus that pending better material, it ma) - be placed here though I 

 incline to believe it belongs rather to some of the allied genera. In Retio- 

 graptus its most marked peculiarity is the great obliquity of the thecae to 

 the virgula. 



On specimens from the same locality, and others from outcrops in the 

 Mohawk valley, I have been able to verify Gurley's observation as far as 

 the mouth ledges and the ascending branches of the parietal ledges are 

 concerned while the structure of the lateral faces is nearly always com- 

 pletely obscured by the thick covering periderm. In badly macerated 

 examples, however, where the continuous periderm is lost, a fibrous layer 

 is sometimes exposed. In one of the specimens, from the Utica shale of 

 Dolgeville \scr pi. 27, fig. 6 1, I have been able to make out, before I was 

 aware of this view, two rows of meshes, one of which corresponds to a row 

 of thecal apertures. This aspect as well as the smooth, flat, heavily covered 

 lateral faces resembles more that of Retiograptus geinit/ianus 

 Hall, as described in this paper than of any other form. Since, however, 

 it is shown here that Lasiograptus and Glossograptus also possess a 

 similar system of libers within their periderm, the question ol the relation- 

 ships of G. quadrimucronatus should It handled most cautiously 



