NO. lO CAMBRIAN FOSSILS, 4TH CONTRIP.UTION RESSER 15 



Lower Cambrian, Hoppin ; North Attleboro, Massachusetts. 

 Holofypc— U.S.N M. no. 96476. 



Helcionella cobboldi, n. sp. 



Stetwtheca abnipta ? Cobbold, Geol. Mag., dec. 6, vol. 4, p. 156, pi. 4, figs. 

 28, 29, 1919. 



This species is similar to H. abnipta, but differs in being more 

 slender and the ribs do not project so far beyond the marginal outline 

 of the shell. 



Lower Cambrian, Hartshill ; Nuneaton, Warwickshire, England. 



Cotypcs. — Sedgwick Mus. 



Helcionella abrupta (Shaler and Foerste) 



Stcnotheca abrupta Shaler and Foerste, Bull. Mus. Comp. Z06I., vol. 16, 

 p. 29, pi. I, figs. 9a, b, 1888; Walcott, loth Ann. Rep. U. S. Geol. Surv., 

 p. 617, pi. 74, figs. 6, 6a, 1891. 



Only the smaller of Foerste's specimens is to be found in the col- 

 lections. These types were never marked and the material is rather 

 fragile. The species must be restricted to the form first described. 



Lower Cambrian, Hoppin ; North Attleboro, Massachusetts. 



Cotypcs. — U.S.N.M. no. 96477. 



Helcionella alia, n. sp. 



Stcnotheca curvirostra Grabau, Occ. Papers Boston Soc. Nat. Hist., vol. 4, 

 p. 638, pi. 31, fig. 13, 1900; Grabau and Shimer (not Shaler and Foerste), 

 N. A. Index Foss., vol. 2, p. T,yT„ fig. i674d, 1910. 



This species is stouter and longer than H. curvirostra and has more 

 numerous ribs. 



Lower Cambrian, Weymouth ; Sandy Cove, Cohasset, Massa- 

 chusetts. 



Holotype. — Boston Soc. Nat. Hist. no. 11964. 



Helcionella grabaui, n. sp. 



Stcnotheca abnipta Grabau (not Shaler and Foerste), Occ. Papers Boston 

 Soc. Nat. Hist., vol. 4, p. 637, pi. 31, figs. I2a-c, 1900; Grabau and 

 Shimer, N. A. Index Foss., vol. 2, p. 373, figs. i674a-c, 1910. 



This is an erect species, but even then is more curved than H. 

 abrupta. Grabau's original figures do not agree one with the other, 

 but angle of view and the difference between mold of interior and 

 exterior would account for this. This species is characterized by the 

 large number of annulations, 10 being shown in the figure. 



Lower Cambrian, Weymouth ; Nahant, Massachusetts. 



Cotypcs. — Boston Soc. Nat. Hist. no. 11962. 



