182 POPULAR HISTOHY OF THE AQUARIUM. 



landj and, from the style of their masonry, of old Cyclopean 

 walls. Even the mason wasps and bees are greatly inferior 

 to these mason Amphitrites." 



Serpula contortuplicata. — (Plate I. fig. 1.) 



The fan-like and pectinated gills of Serpidcs, with their 

 curious stoppers and twisted shelly tubes, give a very lively 

 and animated appearance to an Aquarium. T^'ith the lower 

 part of its shell attached to empty shells, stones, broken 

 glass and pottery, it rears its upper or later circles to an 

 elevation, from which the gorgeous paraphernalia of his 

 head protrude in proud arra}-, or into which they shrink 

 when danger seems to threaten. The tubes, if followed in 

 their twistings, will measure some inches in length, and are 

 about a quarter of an inch or more in diameter. The same 

 lines of growth as are seen in the shells of MoUusca mark 

 the successive additions to its length. The mouth of the 

 tube is slightly expanded, and similar expansions lower 

 down mark wliere successive mouths were formed. Those 

 beautiful fans which you see projected from the tube are 

 gills. They constitute a fringe or frill, open in front and 

 sinuously bent inwards behind. On minute examination, 

 you find each filament of the fringe is a delicately-formed 



