262 NEW YORK STATE MUSEUM 



Position and localities. L. flaccid us mut. trentonensis occurs 

 in excellently preserved specimens, but not in great number in the Nor- 

 manskill shale at Glenmont, with D i p 1 o g r. angustifolius and 

 C r y p t o g r. t r i c o r n i s. In great profusion it is found in a layer of the 

 same horizon at Mt Moreno, forming sometimes bundles of 40 and more of 

 parallel specimens ; the branches extending horizontally in both directions 

 from the sicula [fig. 7]. It is there associated with D i p 1 o g r. foli- 

 aceus and dense masses of Thamnogr. capillaris. The typical 

 expression of the species is on this continent known only from the Utica 

 shale of Lake St John in Canada. It is also a common form in the 

 Hartfell shales of Great Britain where it produces no less than five 

 varieties. 



Remarks. From its general aspect one will unhesitatingly recognize 

 in this mutation the later L e p t o g r. flaccidus and an inspection of 

 the central part and character of the thecae bears out this identification. 

 Moreover are also some of the varieties of the Hartfell shales already 

 developed in the Normanskill shale. Compared with the Utica form, the 

 Trenton mutation is a little thicker, but the difference would seem hardly 

 sufficient to deserve recognition were it not for the occurrence of the New 

 York form in a different formation. 



Leptograptus flaccidus (Hall) var. spinifer Elles & Wood mut. trenton- 

 ensis nov. 



Plate 14, figures 8, 9 



Leptograptus flaccidus var. spinifer Elles & Wood. Monogr. Brit. Grapt. 

 pt 3 (Pal. Soc. 1903). p. 108; pi. 14, fig. 2a-c 



This striking variety differs, according to the original description, from 

 the typical species, " in the mode of origin of its stipes, its more irregular 

 curvature, its longer sicula and the more conspicuous spines on the proxi- 

 mal thecae." The figures here given of the New York specimens distinctly 

 show all of these characters except the budding ol the first thecae. 1 he 

 sicula is very long (2 mm, see tig. 17*)) and gradually tapering. Its aper- 

 ture is furnished with a long, often needlelike, virgella. The first tour 



