No. 89.J 



59 



The specimens of this species which I have seen are usually not more than from 

 one-half to seven-eighths of an inch in length. The axis is narrow; the points of 

 the serrations separated, leaving a defined triangular indentation; and the aspect 

 is that of a contracted or shrunken stipe, and by this character alone is very 

 readily distinguished. It has been observed in considerable numbers, so that we 

 can have no doubt as to the constancy of its characters. 



GrAPTOLITHTJS MARCIDtrS. 



Fig. 1. A specimen more contracted than usual, with the serratures 

 obtuse. 



Fig. 2. An individual presenting a more expanded form, with dis- 

 tinct denticles at the lower extremity and a minute radi- 

 cle below. 



Fig. 3. A young form where the serratures are not developed, or are 

 flattened in the line of their direction, and in which the 

 minute fibres or radicles at the base are well preserved. 

 The specific relations of these forms have not been fully 

 determined ; and I am, at present, unable to refer them 

 to any other than this one. 



Geological position and locality. 

 Albany. 



In the shales of the Hudson-river group : Near 



GRAPTOLITHUS ANGUSTIFOLIUS (n. s.). 



Stipes simple, linear, slender, biserrate; serratures well defined, the denticles short 

 ovate-acute, the extremities sometimes subobtuse; base marked by minute seti- 

 form radicles; midrib projecting beyond the serrated portion in a capilliform 

 extension. Serratures arranged in the proportion of about twenty-eight to 

 thirty in the space of an inch. 



This species has a narrow stipe with very distinct denticles, which are usually 

 closely arranged or apparently overlapping each other at the base, while some- 

 times they are separated more distinctly and the indentation deeper. The form 

 and proportions of these denticles are different from those of any species of Grap- 

 tolite in the collections from these shales, and often more resembling the minute 

 denticulations on the fronds of fossil ferns than those of the graptolites. The den- 

 ticles are often subalternate on the opposite sides of the stipe, and frequently vari- 

 able in the same individual. 

 The accompanying figures illustrate the usual characters of this species. 



Fig. 1. A single stipe, twice the natural size. 

 Fig. 2. A portion still further enlarged. 



This species is associated in the same laminae of slate with G. 

 marcidus, G. whitjieldi, Reteograptus barrandi. 



Geological position and locality. In the shales of the Hudson river group : Near 

 Albany. 



