CRETACEOUS FOSSILS. 191 



Length, 3. inches; width, 1.8 inch ; thickness through both valves, 1 inch. 



A single specimen, from the Nunaimo Coal Mine, Vancouver Island, Chico 

 Group ; kindly loaned me by Mr. Samuel Hubbard,of the Pacific Mail Steamship 

 Company of San Francisco, and to whom I dedicate the species, in recognition of 

 the unostentatious but valuable services he has been rendering to science for a 

 series of years past. 



MYTILUS, Linn. 



M. QUADRATUS, D. 8. 



PI. 31, Fig. 87. 

 (Inoceramus Piochii (pars), Gabb ; Pal. Cal., Vol. 1, pi. 25, fig. 174.) 



SHELL moderate in size, thin, flattened, elongate, rounded 

 quadrate ; beaks small, acute, terminal ; anterior margin very 

 slightly sinuous above, and broadly convex, nearly straight 

 below; posterior side slightly convex and nearly parallel with 

 the anterior; cardinal margin slightly sloping, and uniting by a 

 broad curve with the posterior; base broadly convex, most promi 

 nent anteriorly. Surface slightly but regularly convex, except 

 close to the anterior margin, where it falls more rapidly; orna 

 mented by a few irregular lines of growth. 



Figures, natural size. 



From the Chico Group, at Martinez and Tuscan Springs. 



In my original description of "Inoceramus" Piochii, I supposed this to be the 

 smaller valve of that species, and accordingly included it. As will be seen further 

 on, however, both valves of that shell are very different from the present one. 



The present species can be at once distinguished from all other Mytili by its 

 unusually square form. Its nearest ally is M. ascia, but that shell is arched, and 

 the more slender form and acute anterior end will sufficiently separate them. 



MODIOLA, Lam. 

 M. MAJOR, n. s. 



PI. 31, Fig. 88. 



SHELL very large, thick, slightly curved ; beaks small, about 

 an eighth of the length from the anterior end, which is narrowly 



