THE PRIMORDIAL, OR CAMBRIAN AGE. 39 



with fossils. These are no longer mere Protozoa, but 

 include representatives of all the great groups of ani- 

 mals which yet exist, except the vertebrates. We 

 shall not attempt any systematic classification of 

 these; but, casting our dredge and tow-net into the 

 Primordial sea, examine what we collect, rather in the 

 order of relative abundance than of classification. 



Over great breadths of the sea bottom we find vast 

 numbers of little bivalve shells of the form and size 

 of a finger-nail, fastened by fleshy peduncles imbedded 

 in the sand or mud; and thus anchored, collecting 

 their food by a pair of fringed arms from the minute 

 animals and plants which swarm in the surrounding 

 waters. These are the Lingulce, from the abundance 

 of which some of the Primordial beds have received 

 in England and Wales the name of Lingula flags. 

 In America, in like manner, in some beds near St. 

 John, New Brunswick, the valves of these shells are 

 so abundant as to constitute at least half of the 

 material of the bed; and alike in Europe and 

 America, Lingula and allied forms are among the 

 most abundant Primordial fossils. The Lingulas are 

 usually reckoned to belong to the great sub-king- 

 dom of mollusks, which includes all the bivalve and 

 univalve shell-fish, and several other groups of crea- 

 tures; but an able American naturalist, Mr. Morse, 

 has recently shown that they have many points of 

 resemblance to the worms ; and thus, perhaps, consti- 

 tute one of those curious old-fashioned "comprehen- 

 fiive JJ types, as they have been called, which present 



