90 



THE CAMBRIAN. 



[bull. 81. 



of the Olenellus zone, as found in the vicinity of Troy, New York. The 

 species described are : 



Obolella crassa, var. 



Obolella (?) 



Fordilla troyensis. 



Lamellibranch (?) 



Scenella reticulata. 



Steuotheca rngosa, var. panpera. 



S. ragosa var. abrupta. 



S. curvirostra. 



Platyceras primseviim. 



Plenrotomaria (Raphiatoma) attle- 



boreusis. 

 Hyolithes quadricostatns. 



H. communis var. emmonsi. 



H. americaims. 



H. princeps. 



H. billingsi. 



Ilyolitliellns micana. 



Salterella curvatus. 



Aristozoe. 



Microdiocus bellimarginatna. 



M. lobatus. 



Paradox ides walcotti. 



Ptycboparia mncronatus. 



Ptyciioparia attleborensis. 



Of these, two genera— Plenrotomaria and Paradoxides— have not 

 heretofore been found in a strongly marked Olenellus zone fauna. A 

 comparison of Paradoxides walcotti with specimens of Olenellus asa- 

 phoides from Troy, New York, of the same size, show them to be generi- 

 cally, if not specifically, identical. This removes Paradoxides from the 

 Olenellus fauna. 



Under the view that the Olenellus fauna preceded the Paradoxides 

 fauna Prof. Shaler 1 speaks of Paradoxides ivalcotti as the surviving 

 member of the series, and says the occurrence of the genus indicates 

 close affinities with the Brain tree Cambrian horizon. He made careful 

 search for indications of the stratigraphic relations of the North Attle- 

 borough and Braintree section but without success. In mentioning the 

 Braintree locality it is stated that a number of distinct remains occur 

 near the Neponset River, and the beds have much the same aspect and 

 are apparently about the same distance from the syenites as those at 

 Braintree. 2 



A notice and description of the fauna found at North Attleborough 

 from the Olenellus horizon, was followed in 1889 3 by the announcement 

 of the discovery of Hyolithes in limestone near East Point, Nahant. 

 Mr. Foerste correlates the limestone and associated shales with those 

 of North Attleborough, and states that the species of Hyolithes appear 8 

 to be the same as that found at North Attleborough. He proposes the 

 name of Hyolithes ina^qui lateralis. From a study of the type specimens 

 the writer believes it to be identical with H. communis var. emmonsi. 



As now known, the entire Cambrian fauna from eastern Massachu- 

 setts includes from the Paradoxides or Middle Cambrian zone four 

 genera and four species, and from the Olenellus or Lower Cambrian 

 zone, twelve genera and nineteen species. 



1 On the geology of the Cambrian district of Bristol County, Massachusetts. Bull. Mus. Comp. Zool., 

 Harv. College, vol. 16, 1888, p. 21. 



2 Op. cit., p. 23. 



3 Foerste, A. F. The paleontological horizon of the limestone at Nahant, Massachusetts. Boston 

 Soc. Nat. Hist., Proc, vol. 24, 1889, pp. 261-263. 



