BILLINGSELLID^. 745 



shell, free spondylium and absence of cardinal process, it is allied closely to Protorthis; the 

 depressed ventral valve and convex dorsal valve serve to distinguish it as a subgenus of Pro- 

 tortTiis. 



The specific name is derived from Dugald Brook, Cape Breton. 



Formation and locality. — Middle Cambrian: (lOy) Sandstone just beloiu the waterfall 0J5 mile (0.4 hm.) from, 

 the lower bridge in Division E2b of Matthew's [1903, p. 2f\ Etchemvnian, Dugald Brook, Indian River, eastern Cape 

 Breton, Nova Scotia. 



(2u) Lowest beds exposed on the south side of Long Island, Kennebecasis Bay [Matthew, 1898a, pp. 124 and 

 127], St. John County, New Brunswick. 



Subfamily BILLINGSELLIN^ Schucliert. 



Genus WnVtANELLA Walcott. 



Billingsella Walcott (in part) [not Hall and Clarke], 1905, Proc. U. S. Nat. Mus., vol. 28, pp. 227-229. (Described 

 and discussed as on p. 749 (under Billingsella), but several of the species referred to the genus are now placed 

 under Wimanella.) 



Wimanella Walcott, 1908, Smithsonian Misc. Coll., vol. 53, No. 3, pp. 98-99. (Discussed somewhat as below as a 

 new genus.) 



f^imanella Walcott, 1908, idem, vol. 53, No. 4, PI. XI, and pp. 142 and 148. (Classification of genus.) 



This genus is proposed for the smooth nonplicate species that I have heretofore referred 

 to the genus Billingsella. The generic description of Billingsella includes the characters of 

 Wimanella with the exception that the latter is a smooth shell but for the presence of concentric 

 striae and lines of growth. Wimanella represents the smooth, early stages of development 

 and Billingsella the later, mature plicate stage of development of this section of the BillingsellidjE. 



Type. — Wimanella simplex Walcott [1908d, p. 98]. 



Observations. — It is to be noted that Billingsella plicatella Walcott (PI. LXXXVI, figs. 3g 

 and 3h) includes some shells that are nearly smooth, and that B. higlilandensis (Walcott) (PI. 

 LXXXVII, figs. 4 and 4c) is very finely costate. The former species may be considered as 

 being in part a form intermediate between Billingsella Colorado ensis (Shumard) and Wimanella 

 Tiarlanensis (Walcott) . I think, however, that the species with smooth shells should be grouped 

 under a generic head, as they indicate a marked phase in the evolution of the forms formerly 

 grouped under Billingsella. 



The generic name was given in recognition of the valuable work of Dr. Carl Wiman of the 

 University of Upsala, on the geology and paleontology of the Baltic region. 



Wimanella? anomala (Walcott). 

 Plate LXXXVII, figmres 1, la-e. 



Billingsella? anomala Walcott, 1905, Proc. U. S. Nat. Mus., vol. 28, p. 230. (Described and discussed as below as a 

 new species.) 



Shell subquadrilateral, with the dorsal valve transverse. On the ventral valve the cardinal 

 line slopes towar-d the beak at an angle of from 15° to 20°, while in the dorsal valve it is nearly 

 straight. The greatest width of the valves is about the middle of the shell. Owing to com- 

 pression and consequent distortion there is considerable variation in the relative proportions of 

 length and breadth. The cardinal angle is acute, in some instances extending out some distance 

 beyond the widest portion of the shell, resembling in this respect the cardmal angles of some 

 of the Strophomenidse. All of the specimens are so compressed in the shale that little is 

 preserved of their natural convexity. A low, broad, mesial sinus occurs on the dorsal valve, 

 and there is a shght flattening of the anterior central portion of the ventral valve. 



The surface is marked by fine, radiating striae, that are increased in number toward the 

 front by the addition of interstitial strife, giving a fasciculate appearance to the surface. The 

 radiatiug striae are crossed by concentric lines of growth and fine striae. The surface as described 

 occurs in one specimen, all other specimens being nearly smooth. This, however, may arise 



