GRAPTOLITES OF NKU YORK, PART 2 413 



mucro [see fig. 364]; rhabdosome attaining its full width (1.8 mm) within 

 3 mm, its margins parallel thereafter. A free prolongation of the nema- 

 caulus mostly present, attaining half the length ot the rhabdosome. First 

 one or two pairs of thecae narrow and appressed to nemacaulus as in C. 

 typical is; later thecae bent twice; the middle part directed obliquely 

 outward and the proximal and distal parts subparallel to axis of rhabdo- 

 some. Aperture normal to distal part of theca ; interthecal excavation long 

 (one third the length of theca) but shallow (one fourth width of rhabdo- 

 some) ; subtriangular in outline. Thecae numbering 12 in 10 mm (30 in 1 

 inch). 



Formation and locality. The specimens were obtained by 

 Dr Ulrich in the Maquoketa shale at Spencer, 20 miles south of 

 St Louis, Mo. 



Remarks. This, the latest Champlainic American Climaco- 

 graptus known to the writer, presents some interesting features. 

 Its sicular end is that of a C. typical is, while in 

 its general habit and size it reminds of Diplogr. 

 p e o s t a. The restriction of the narrow, appressed 

 form of the thecae to two pairs and the rapid, some- 

 times even abrupt widening of the rhabdosome beyond 

 these suggest a tachygenetic process and that C . F ; g 



.... , , . , r , , tus ulrich i sp. nov.° Fig. 



ulrichi may be a last remainder 01 the stock of 3<h 4 y P e specimen. Fig. 365 



J faicular end of another speci- 



C . t y p i c a 1 i s. The later thecae are greatly different 



from those of C. typical is and would by the slightly oblique marcrins 

 of their distal parts indicate a form with less typically climacograptid thecae 

 than the genotype. The specimens are so badly flattened that neither the 

 character of the lateral faces nor the presence or absence of a septal o-roove 

 could be determined. 



Climacograptus mississippiensis sp. nov. 



Plate 28, figures 12, 13 



Description. Synrhabdosomes not observed. Rhabdosomes small, 

 maximum length observed 15 mm, length of majority of specimens 7 to 



64 



