CONCHOLOGY. 27 
D. octogonum. D. corneum. 
D. deforme. D. nigrum. r 
D. novemcostatum. D. politum. 
D. sexangulaire. D. eburneum. 
D. striatum. -D. clava. 
D. dentalis. D. fissura. 
D. coarctatum. 
FAMILY III. 
AMPHITRIT=HA. Four Genera. 
1. Genus Pectinaria. PI. V. 
Animal. Respiratory organs in general known, and disposed 
at or near the anterior part of the body ; not separated or covered 
by an operculum. 
Shell. A membranous papyraceous tube in the form of a 
reversed cone; unfixed; exterior covered with sandy adhesions. 
Two species. 
Pectinaria capensis. 
P. belgica.* 
2. Genus Sadellaria. Pl. V. 
Animal. But slightly differing from the Pectinaria. 
Shell. ‘Tubes numerous, united in a common mass, composed 
of agglutinated particles of marine substances, cellular at the 
base; orifice expanded. Found in the Indian Ocean. Two 
species. 
Sabellaria alveolata. Sabellaria crassissima. 
3. Genus T'erebélla. Pl. V. 
Animal. Body tubicular, elongated, cylindrically depressed, 
attenuated posteriorly ; a row of nodulous and setiferous papill« 
on each side ; numerous filiform, twisted tentacula surrounding the 
mouth. 
Shell. An elongated cylindrical and membranous tube with 
