246 



Annals of the Carnegie Museum, 



The shells vary in outline; some are wider than long, while in others 

 the width and length are about equal. The sides are rounded, and 

 the front is nearly straight in some specimens and rounded in others. 



19 20 



Fig. 19. Heberlella bellariigosa (Conrad). A brachial valve. X 2. 

 Fig. 20. The same species. An imperfect brachial valve, to show the strong 

 concentric lamellae. X 2. 



Locality. — A rather common shell in two localities on Valcour 

 Island, New York. 



28. Orthis acuminata Billings. 



Orthis acuminata Billings, 1859. Canadian Naturalist and Geologist, Vol. IV, 



p. 44, fig. 19. 

 Orthis acuminata Billings, 1863. Geology of Canada, p. 130, fig. 59. 



This species, which is characterized by its Spirifer-Vike outline, was 

 founded by Billings on a single specimen from Caughnawaga, Canada. 

 The type is now before the writer, and it proves to be an imperfect 



Fig. 21. The type of Orthis acuminata Billings. Outline drawing to show 

 the portion of the shell now preserved, and its probable shape when complete. 

 One-half larger than natural size. 



Fig. 22. Interior of a brachial valve of Hebertella vulgaris, to compare with 

 the preceding. 



brachial valve of some species of Hebertella, perhaps H. vulgaris. 

 The acuminate character of the cardinal extremities is due to a trans- 

 verse fracture of the shell and the flaking off of some of the inner layer. 

 The shell is broken very evenly along the front, but that it is broken 



