34 CONCHOLOGY. 



CLASS III. 



CONCHIFERA. 



Animals. Soft, inarticulated, always fixed in a bivalve shell, 

 without head or eyes, having the mouth naked, concealed, and 

 without any hard parts ; a large mantle enveloping the whole of 

 the body, forming two laminiform lobes, the edges detached or 

 sometimes united in front. Gills or respiratory organs external, 

 situated on each side between the body and the mantle ; circula- 

 tion simple, the heart with one ventricle ; some few ganglions of 

 the different nerves, but no knotted medullary cord. 



Shell. Always bivalve, enveloping the animal entirely or par- 

 tially, sometimes free, sometimes affixed ; the valves most fre- 

 quently united on one side by a hinge or ligament, sometimes 

 attached to the shell, are testaceous accessory pieces. Twenty 

 families. 



FAMILY I. 



TuBicoi.A. Six Genera. 



1. Genus Jlspergillum. PI. V. 

 Animal. Entirely unknown. 



Shell. Oval, somewhat elongated, striated longitudinally, conic, 

 club-shaped, open at its attenuated extremity, and terminated at 

 the other by a convex disk, pierced by a number of small perfo- 

 rations, and encircled by a dilated margin of papyraceous tubes, 

 resembling a plaited ruff, smaller extremity always open. This 

 is a well known, but rare shell, found in sandy places in low 

 water in the Indian ocean. Four species. 



Aspergillum Javanum. Aspergillum Novae Zjelandise. 



A. vaginiferum. A. agglutinans. 



2. Genus Clavagella. PI. VI. 

 A7umal. Unknown. 



Shell. A tubular sheath, testaceous, attenuated, and open before ; 



