GRAPTOLITES OF NEW YORK. PART 2 427 



majority of specimens 20 mm long (maximal length observed is 32 mm) 

 rapidly attaining" (in length of five to six thecae) its full width which is 1.5 

 to 2 mm. Sicular extremity possessing a long rodlike virgella (6.5 mm 

 long) with a broad basal membrane (or prolongation of the opposite lappet 

 of the sicula ?) and two short straight horizontal lateral spines. Antisicular 

 end truncate, not narrowing. 



Nemacaulus thin, but rigid and long ; frequently possessing in mature 

 specimens a vesicle, which varies in form from narrow lanceolate to broadly 

 elliptic, attains a maximal length of 10 mm and a width of 4 mm and is not 

 situated terminally. Sicula slender, about 1.3 mm long. Thecae numbering 

 12 to 15 in 10 mm ; in the usual, completely flattened state showing straight, 

 or slightly concave outer margins of the distal free parts, which appear as 

 squarish projections between the deep elliptical horizontal excavations, 

 that occupy about one third of the ventral margin and in mature speci- 

 mens one third the width of the rhabdosome. In specimens showing full 

 relief [see fig. 393] the proximal part of the theca is seen to be narrow and 

 parallel to the axis, the ventral wall of the distal free part is slightly inclined 

 inward and the apertural margin slightly introverted. The overlap is not 

 much more than one third the length of the theca. The septum extends 

 the greater length of the rhabdosome. 



Position and localities. Hall listed C. parvus as one of the forms 

 of the " Hudson River formation." Gurley records it as occurring at Stock- 

 port, Columbia co., N. Y. and calls it one of the most characteristic forms 

 of the Lower Dicellograptus zone (Normanskill shale). The writer has 

 observed it in collections from numerous outcrops of the same zone in the 

 slate belt of New York, especially in those from the Normanskill and 

 Glenmont near Albany ; Mt Moreno near Hudson ; Castleton ; Schodack 

 Landing ; Mt Olympus and Poestenkill at Troy ; Granville in Washington 

 county, etc. This species has not been recognized by the Canadian geol- 

 ogists and is not cited by them, but undoubtedly extends with the Dicello- 

 graptus fauna through Vermont into the St Lawrence region. Outside of 

 the Levis channel the form has not yet been found or recorded. 



