GRAPTOLITES OF NEW YORK, PART 2 



409 



I 



360 



354 



thecae of the mature part of the rhabdosome is very characteristic, their 

 distal free parts standing out as series of squares from the broad median 

 part of the lateral face. This squarish aspect of the thecae is, besides their 

 straight apertures and straight outer margins especially due to their equally 

 straight outer walls opposite the 

 apertures of the preceding thecae. 

 This geniculated part of the thecal 

 wall is so much thicker than the 

 others that it clearly stands out above 

 the latter and in some specimens it is 

 even produced into a mucro [see text 

 fig. 354]. In all other congeners this 1 

 part of the thecal wall is very dis- 

 tinctly concave or depressed. 



From C . b i c o r n i s, with which 

 it ma)' be found associated, it differs, 

 aside from the absence of the lateral 

 spines, in the narrower sicular ex- 

 tremity, the more rapid and less uni- 

 form widening' of the rhabdosome 

 and the wider apertural excavations. 

 The only species of Climacograptus Fi g . 3 limacograptus t yP icaii Hail. 



Copy of one of Hall's original figures, representing a longitudi- 



in the graptolite shales of New York ^L^^od^Ms^n^^^^/t ^ 



. .... 1 - frig. 357 Sicular end of a slightly different mutation in shale 



that pOSSeSSeS a Similarly Slender dredged from river at Troy, _N. Y. Fig.3s8 Mature portion of 



1 J rhabdosome of typical specimen from Holland Patent, N. Y. 



i •, ■ /-< i , Fig 359-61 Mature portion and sicular extremities of speci- 



SlCUlar extremity IS L- . C a ll Cl a t U S. mens from lower third of Eden shale at Covington, Ky. (Ulrich 



coll.). Fig. 362 Portion of variety from Lees Gulf, Lewis co., 



This goes still beyond C. typi- N-Y - xs 



c al i s in the slenderness of its rhabdosome and attains its maximal width 

 much slower. C. parvus has squarish thecae like C. typical is, but 

 it can for this reason not yet be considered as a dwarfed mutation of 

 C . ty pi cal i s, as Freeh has done [1897, p. 6 10] ; for it precedes the latter 

 and is separated from its horizon by the zone of Diplograptus amplexicaulis 

 in which it is absent, and it has a greatly different rhabdosomal outline. 



355 



