S U M MARY 
or THE 
GENERA OF CORNISH TESTACEOUS MOLLUSCS. 
SEDENTARY ANNUL AT A : With tubes or cases, encrusted with 
grains of sand and fragments of shells ; or solid, calcareous and 
homogenous. This order comprizes Dentalium, Sabeiluria, Tere- 
hella. Amphitiite, Spirorhis, Serpnla, Vcrmilia. Vermetus much 
resembles the Serpulaccse, but is separated on account of the different 
c, structure of tlie animal. 
"RHIPEUA, ok BARNACLES ; With many valves or plates, sessile 
°r on a footstalk. From an opening capable of being closed proceed 
many slender, jointed, fringed tendrils, which are organs of prehen. 
“ion. It comprizes Tubicinella, Balanus, Acasta, Creusia, Pyrgoma, 
Which are sessile ; and, with footstalks, the Genera Auatifera and 
pr. follicipes. 
•' j NCHIFERA on BIVALVES : With two principal valves or plates 
United by a hinge or ligament ; and sometimes with accessary plates 
not belonging to the valves. It is divided into two orders; C 011 - 
phifera Bimuscnlosa, with two internal separate and lateral muscnlar 
hnpressions ; and Conchifera Unitmtsoulosa, with only one. muscle, 
which appears to pass through the body : the impression being about 
’ho centre of the shell. 
£ Tlte first order, C. Bimuscu/osa, comprizes four Sections, 
^■Ussipeba : The shell when shut, gaping at the sides : Comprizing 
(j ’he Genera Teredo, Pholas, Gastrochama, Solen, Mya, Anatina. 
' ’vnuipeda: Gaping of the shell at the sides generally little: Com- 
prizing the Genera Lutraria, Mactra, Auiphidesma, Corbula, 
^axicava, Vcnerirupis, Sangniuolaria, Psamonobia, Tellina, Lttcina, 
C I ’- ) onax, Capsa, Crassina. 
■ ’a'Mei.i.ipkda : Gaping none, but it. is chiefly distinguished by the 
structure of the animal : the foot being broad and thin : Comprizing 
’he Genera Cyclas, Pisidium, Gyprina, Cytherara, Venus, Cardium, 
C Riatellit, Iso-cardia, Area, Pectttnculus, Nucula, Uttio. 
Avibigua on ciiahacea : The valves unequal, irregular: the hinge 
w >th one thick toollv, or toothless The genus Isocardia was 
'Nan prized in this section, hut is now removed ; there remains in it 
therefore, no British species. 
27ie second order, C. Unimusculosn comprizes three Sections, 
edg* 16 ht'St, with the Ligament marginal, sttblinear, elongated on the 
C . comprizing tile Genera Modiola, Mytilus. Pinna, Avicnla. 
the k° n 'L Ligament not marginal, contracted into a short space below 
v a!vp ks ’ visible, and not forming a tendinous cord under the shell; 
^ecte Une 4 l * a L either in size or sliape. It comprizes the Genera Lima, 
fk: 11 ! Ostrea, Anomia. 
shell . * ligament none, or formed by a tendinous cord supporting the 
comprizing the Genus Terebratula. 
