Moll. 87 
BIVALYIA, MONOMYARIA. 
impressions ; pallial line sinuated. Pholadomyidce , Oorbulidce , 
My idee, Anatinidce , Mactridce , Paphiidce , Glycymeridce , ? Sole- 
nidee , and all Tubicola. 
Ord. 3. Taxodonta. Teeth of the hinge numerous, not differen- 
tiated, in a straight, arcuated or angular row ; two equal muscu- 
lar impressions. Arcidce, Nuculidce. 
Ord. 4. Heterodonta. Teeth of the hinge few, distinctly sepa- 
rated as cardinal and lateral, alternating, exactly filling the 
pits of the opposite valve ; two equal muscular impressions. 
Unionidce, Cardiniidce, Astartidce , Grassatellidce , Megalodontidce , 
Chamidce , Tridacnidce , Erycinidce , Lucinidce , Cardiidce, Oyrenidce , 
Oyprinidce , Ferceridce, Gnathodontidce , Tellinidce , Donacidce. The 
Trigoniidce will form a distinct suborder. 
Ord. 5. Anisomyaria, or Dysodonta. Teeth of the hinge none or 
irregular ; two very inequal or only one muscular impression ; 
pallial line entire. 
(a) Heteromyaria : Aviculidce, Mytilidce, Prasinidce, Pinnidee. 
(b) Monomyaria: Pectinidce , Spondylidce , Anomiidce , 
Ostreidcc . 
He thinks that Desmodonta , Trigonidce, and Taxodonta may be directly 
derived from the Palceoconchce ; that the Taxodonta may have been 
further developed into the Heterodonta and Heteromyaria ; and that the 
Monomyaria are derived from the latter. SB. Ak. Wien, lxxxviii. Abth. 1, 
pp. 385-419, 2 pis., representing the hinges of various recent and fossil 
genera. [This proposal has several considerable advantages in compari- 
son with hithorto accepted classifications, viz. : — (1) Tho distinction of a 
limited number of natural types, instead of an artificial separation into 
Monomyaria and Dimyaria , or Asiphonida and Siphonida ; (2) the union 
of the Heteromyaria and the Monomyaria into one common chief divi- 
sion ; (3) the constitution of a special chief division for the Arcidce and 
Nuculidce , as these families offer very peculiar characters as well in the 
shell as in the gills and foot, and have hitherto been placed either 
between the Aviculidce and Mytilidce , or between the Mytilidce and Unio- 
nidce, disturbing in each case a natural series. But it may be regretted 
that the author has not given any regard to the more important diffe- 
rentiated characters of the soft parts ; and it is by no means certain 
that either the Mactridce and Veneridce, or the Paphiidce and Donacidce , 
are so very deeply different inter se , or that they originate from such 
different sources, as the author endeavours to make out. The new terms 
of orders and suborders will, however, be used in the following Record, 
as this classification is more convenient than that formerly followed. — 
Rec.] 
MONOMYARIA. 
OSTREIDAC. 
Ostrea. P. P. C. Hoek gives a very accurate and long list of works 
and papers relating to the oyster, as well those conchologically descrip- 
