374 



NEW YORK STATE MUSEUM 



lograptus shale" | Sardeson] of the Maquoketa beds in Minnesota, Wiscon- 

 sin and Iowa. It also occurs, though rarely, in the Lorraine beds of New 

 York and Hall's type of D . p r i s t i s , v. i, pi. 72, fig. if, ig [see text figure 

 319] from the "Hudson River group" at Lorraine presents all the 

 characteristic features of this species. 



Remarks. D. peosta is in its general habit and the form of the 

 thecae a smaller D. amplexicaulis but attaining neither the length 

 nor width of that species and differing in the form of its cross-section ; while 

 both have in common the alternate imbrication of the thecae on the lateral 

 sides, and the closeness of their arrangement. The Lorraine specimens 

 have as a rule been identified with D . a m p 1 e x i c a u 1 i s, 1 and Hall's type 

 of figures if and 1 g is on exhibit as D. am p 1 e x i c a u 1 i s in the Ameri- 

 can Museum of Natural History. From the equally narrow D. amplexi- 

 caulis var. pertenuis here described, it differs in the much smaller 

 length of the rhabdosome and the somewhat wider arrangement of the 

 thecae. 



Since Hall never figured his species 2 we can not wonder that in the 

 west it has also failed to be recognized, and that the western paleontologists 

 have identified it either with D . amplexicaulis (see James loc. c/7.) or 

 with D. prist i s as Winchell and Schuchert have done, who cite the 

 latter species from Granger, Minn., Cincinnati and Graf, Iowa, and repro- 

 duce Hall's figure ia, which represents an equally small Lorraine mutation 

 of D . f o 1 i a c e u s. 



1 J. T. James records D . a m plexicaulis from the Maquoketa shale [Amer. Geol. 

 4: 237]; Walcott mentions it as being found in the upper part of the Lorraine section [1S90, 

 p. 339] and Whitfield and Hovey enumerate in their type catalogue [Amer. Mus. Nat. Hist. 

 Bui. 1898, v. 11, pt 1, p. 20-21] as D. amplexicaulis a number of Hall's types of 

 Graptolithus prist is of Pal. N. Y. v. 1 from Turin, Lorraine and Collinsville and 

 the present writer has commented [N. Y. State Mus. Bui. 42, p. 561] on the reappearance 

 of 1). amplexicaulis in the Lorraine formation. 



2 A figure of 1). peosta was not published until 1X95, when Whitfield figured the 

 types of Hall's Wisconsin Report. 



