GRAPTOLITES OF NEW YORK, PART 2 $77 



compressed specimens, such as the; figured one is, the other axes are occa- 

 sionally exposed. It is therefore legitimate to conclude that there existed 

 in G. ciliatus a main axis as in the Retiolitidae that corresponded to 

 the nemacaulus of the Diplograptidae [with included virgula] ; and also 

 several lateral axes. There are no lateral axes of an)- kind known in the 

 Diplograptidae ami the presence of such in Glossograptus will further sup- 

 port the exclusion of this genus from that family. In regard to the Retio- 

 litidae Tullberg, Tornquist and Holm have demonstrated the presence of a 

 straight main axis and of an opposite zigzag shaped secondary one ; while 

 Wiman [1895, p. 42] has found that in Retiolites nassa [see text 

 fig. 453] the rhabdosome is supported, aside from the nemacaulus, by four 

 " Hauptleisten " running along the four margins of the prism. Since the 

 thecae occupy the full width of the frontal sides, these "Hauptleisten" 

 must be composed of the lateral ledges of the thecal apertures and of 

 ledges bounding the ventral faces of the thecae [see Wiman's fig. 7]. 

 Retiolites nassa has the thecae of a Climacograptus (and has for 

 this reason been made the type of a new genus, Gothograptus, by Freeh) 

 while our form has those of a Diplograptus. Taking proper notice of this 

 difference, it is to be expected that in Glossograptus the sections of the 

 " Hauptleisten," consisting of the edges of the ventral faces of the thecae 

 are reduced to almost nihil and the lateral ledges of the apertures alone 

 compose the " Hauptleisten," which fact is apparent in plate 27, figure 3. 

 There must further be found in Glossograptus altogether four vertical main 

 ledges besides the nemacaulus, two bounding either row of thecae. These 

 can indeed be made out in the figured specimen [pi. 27, fig. 5], since its 

 margins have also the character of stronger longitudinal fibers. Of these 

 that on the left hand side is distinctly composed of sections of ledges, 

 evidently the lateral ledges of apertures. 



The combined presence of a retioloid layer and of four main ledges 

 warrant the translation of Glossograptus from the Diplograptidae to the 

 Retiolitidae, though Glossograptus evidently partakes of the nature of a 

 transitional form between the two on account of its strong periderm. One 



