476 NEW YORK STATE MUSEUM 



specimens only the bases of the appendages are preserved and appear as 

 mucros, which mostly are flaccid and bent, but sometimes fully as straight 

 and horizontal [see pi. 29, fig. 17] as in Glossograptus whitfieldi 

 and thereby may lead to confusion with that species. There are always 

 two mucros below the aperture of each theca. In L. mucronatus 

 these remain so close together [see pi. 31, fig. 2] that but rarely they appear 

 double, while in L. bi mucronatus [see pi. 30, fig. 5] they diverge at 

 once and thereby show their paired character quite distinctly. Neverthe- 

 less specimens are frequent [as the original of pi. 29, fig. 12] where one 

 portion is distinctly mucronate and another bimucronate, while in a third 

 the mucros may be so rigid and horizontal that it has the appearance of a 

 G. whitfieldi [pi. 29, fig. 17]. 



In specimens where more than the stronger bases of the appendages 

 are preserved, very different aspects are possible. In most of them long 

 fibers, often bearing tufts of finer fibers [pi. 30, fig. 6-3 ; text fig. 459, 462] 

 or in some cases with patches of reticulate tissue [pi. 30, fig. 1] are pro- 

 ceeding more or less horizontally from the rhabdosome. In man)- others, 

 especially of L. mucronatus, these fibers are more completely preserved 

 [pi. 29, fig. 18 ; pi. 30, fig. 4]. Each is seen to recurve to the preceding one 

 and to fasten itself to the same, whereby a double festoon originates. This 

 is subparallel with its outer margin to the rhabdosome, the margin mostly 

 consisting of convex segments, but sometimes also being rigidly straight. 

 In a number of specimens of L . mucronatus [see pi. 30, fig. 5] the par- 

 allel bases of the two fibers of each theca remain connected by a periderm, 

 thereby forming a tonguelike process.' This periderm does not end 

 abruptly at the distal end, but fades very gradually thereby indicating 

 that it extended still farther out. Indeed other specimens [see pi. 31, fig. 2] 

 retain patches of periderm near the outer margin of the festoon and in 

 others [see pi. 30, fig. 8] the triangular peridermal extension can be directly 

 traced between the diverging fibers to near the outer margin, the fibers 



1 This is one of the reasons that L . mucronatus so rarely appears bimucronate in 

 the shale. 



