424 THE CANADIAN NATURALIST. [DeC. 



horny bivalve shell, with one valve, the dorsal, smaller than the 

 other, the beak of which projects and has a notch (foramen) 

 below, through which passes a stalk or pedicel for attachment. 

 The interior of the shell is lined with the two valves of the 

 mantle, and is occupied principally with the two-fringed and 

 ciliated arms coiled like cork-screws. (Fig. 94.) At the base 

 Fig. 94. 



a 



Rhynchonella psittacea. Interior of dorsal valve, showing (a) adductor 

 muscles, and (6) spiral arms ; drawn from a specimen dredged at Gaspe — 

 natural size. 



of these is the mouth, leading to a small stomach and short in- 

 testine. It has a more complicated nervous and circulating 

 system than those of the Tunicates, and has several pairs of 

 muscles placed near the hinge for opening and closing the shell 

 and regulating the movements of the creature on its pedicel. 

 The Rhynchonella is found attached to stones and dead shells in 

 moderately deep water. 



In addition to this species, we have on our coasts Terehratulina 

 septentrionalis, of more elongated form than the above-named 

 species, ribbed longitudinally, with a round perforation at the 

 beak, instead of a notch, and with an internal shelly loop. Other 

 species found on our coasts are Waldheimia cranium, and Tert- 

 hratella Spitzhergensis, a northern form found in Labrador, and 

 also fossil in the post-pliocene clay of Riviere du Loup. Wald- 

 heimia cranium has as yet been found only on the coast of Nova 

 Scotia, by Willis. It has been ascertained that the young of 

 some Brachiopods much resemble Polyzoa in form and structure. 

 (Morse). 



Though recent Brachiopods are few in species, vast numbers 

 are found fossil. Mr. Billings's catalogues include nearly 100 

 species, from the lower Silurian alone, in Canada; and Dr. 

 Bigsby, in his Thesaurus Siluricus, enumerates 429 species from 

 the Silurian of America, whereas leps than 100 living species are 

 known in the whole world at present. 



