208 



TEREBRATULID^. 



valve fitting between two in the lower, wliicli has also slight earlike 

 prolongations ; a stem arises from each side of the hinge, uniting 

 with its opposite, and bearing a short, nearly circular loop for the 

 support of the arms. 



Fig 500. 



Terebratulina septentrionalis. 



Shell obovate, whitish, upper valve truncated horizontally at the apex ; foramen 

 large, one side completed by the apex of the lower valve ; surface with minute, 

 radiating strife. 



Terebratula septentriomiUs, Cocthout, Bost. Journ. Nat. Hist. ii. C5, pi. 3, fig. 18. — 



Stimpson, Mar. Invert. Gr. Manan, 20; Shells of New England, 7. 

 Terebratula caput-serpentis, Gould, Inv. Mass. 1st ed. 141. 



Shell rather thin, semi-transparent, yellowish or reddish-white, 

 broadly obovate ; upper valve slightly convex, narrow at the sum- 

 mit, and abruptly widening below ; beak slightly 

 projecting, truncated horizontally so as to form 

 a large, semi-elliptical orifice, completed below 

 by tlie apex of the lower valve, which valve is 

 rounded, flatfish, slightly protuberant down the 

 middle ; both valves covered by minute, but dis- 

 tinct and well-rounded radiating ribs, which in- 

 crease in number with the width of the shell ; 

 these are crossed by a few irregular lines of 

 growth ; the whole covered by a thin, silvery, 

 fibrous epidermis. From under each tooth in 

 the lower valve arises a thin process curving a 

 little inwards, wdiose extremities sui)port an oval, 

 partially twisted ring of a similar ribband-like structure, about an 

 eighth of an inch in diameter. Margin of the shell minutely toothed 

 by the terminations of the ribs. Length, eleven tAventieths of an 

 inch ; heioht, twelve twentieths of an inch ; breadth, five twentieths 

 of an inch. 



Found in considerable numbers in the stomachs of fish, and occa- 

 sionally on the sea-beach. It has also been taken alive on the coast 

 of Maine. Its usual residence is in more northern seas. 



Lamiimrian to deep sea coral. Eastport at low water, common ; 



off Isle of Shoals, twenty fathoms to Cape Cod ; Grand Manan, 



common (Packard, Stimpson) ; Halifax Harbor, common (Willis). 



An examination of the descriptions of T. caput-serpcniis, given 



T. septentrionalis. 



