FOSSILS OF BELT TERRANE 239 



If we consider figures 1 and 18 of plate 25 as representing a form which 

 ma}' be compared with Pterygotus, and figure 2 of plate 25 and figures 

 4 and 5 of plate 26 as Eur3qDterus, it is possible to consider that the repre- 

 sentative of the Merostomata lived in Algonkian time. The evidence is 

 not conclusive, but I am unable to make as satisfactory comparison of 

 the fragmentary remains with any other crustacean. They certainly do 

 not belong to the Trilobita. It may be that they represent the ancestral 

 form from which the Trilobita and the Merostomata were derived. 



For the purpose of comparison, some illustrations of recent forms of 

 the Merostomata are given on plate 28. The flattened telson, figure 18 

 of plate 25, may be compared with figures 2 and 6 of plate 28. A much 

 more extended series of comparisons may be made by examining the 

 illustrations of the Merostomata given by Woodward, Hall, and Schmidt.* 

 It is the purpose of this preliminary notice to call attention onl}' to the 

 fact of the presence of a large, highly organized crustacean in Algonkian 

 rocks far below the horizon at which traces of the Merostomata have 

 hitherto been found, the oldest known being from the Utica shale of 

 central New York. 



Beltina danai, n. sp. 



(Plates 25, 26, 27.) 



The general characters of this species have already been referred to in 

 the remarks under the genus Beltina. The particular form to which the 

 specific name is given is that represented b}'' the Pter3'gotus-like telson, 

 figure 18 of plate 25, the body segment represented by figure 3, the head 

 re])resented by figure 1, and the fragments of the chelate appendage rep- 

 resented by figures 13 and 14. 



Formation and localities yielding Beltina danai. — Algonkian, Greyson 

 shales; Deep Creek canyon, near Glenwood, and Sawmill canyon, 4 miles 

 above Neihart, Montana. 



Explanation of Plates 



Pla'I'E 23. — Cryj)tozoon? occidentale. 



Figure 1. — Photograph of a thin-section showing portions of two fragments. 

 Natural size. 



Figure 2. — Enlargement of the lower, smaller fragment shown in figure 1. 



Figures .3, 4. — Photographs of two thin-sections occurring in the same stratum of 

 rock as that represented by figure 1. 



* Monograph of British Fossil Crustacea; Paleontology of New York, vol. iii : Mem. Imp. Acad. 

 St. Petersbourg, seventh series, vol. xxxi. 



XXXV— Bull. Geol. Soc. Am., Vol. 10, 1898- 



