286 SUBTJLA. 



SUB. (under.) Fsed as a prefix and signifying nearly. Thus a 

 bivalve-shell, the valves of which are nearly alike, would be de- 



■ scribed as s^S-equivalve. 



STJB-APLTSIACEA. Bl. The first family of the order Mono- 

 pleurobranchiata, Bl. containing several genera of Mollusca 

 without shells, and the genus Pleurobranchus. 



SUB-BIYALVES. A term of distinction applied by De BlainviUe, 

 to those spiral univalves which have an operculum ; these, as 

 they constitute two distinct pieces, he considers as forming a 

 medium between univalves and bivalves. 



SUB-MTTILACEA. Bl. The sixth family of the order LameHi- 

 branchiata, Bl. the shells belonging to which are described as 

 free, rather pearly, regular, equivalve ; hinge dorsal, laminated ; 

 ligament external ; two muscular impressions ; palleal impression 

 not sinuated. This family, vdth the exception of the last genus, 

 agrees with the family Wayades of Lamarck, and contains the 

 genera Anodon, Unio, and Cardita. 



SUB-OSTBACEA. Bl. The second family of Lamellibranchiata, 

 Bl. the shells of which are described as of a compact texture, 

 sub-symmetrical ; with the hinge rather complex ; one single, 

 sub-central, muscular impression, without any traces of palleal 

 impression. This family corresponds with the Pectenides of 

 Lamarck, and part of the genus Ostrea in the system of Linnaeus. 

 It contains the genera Spondylus, Plicatula, Himnites, Pecten, 

 Pedum, Lima. 



STJB-SPIEAL. Not sufficiently spiral to form a complete 

 volution. 



STJBTJLA. Bl. {An awl) A generic name under which M, De 

 Blainville includes Teeebba maculata, Auct. f. 428, together 

 with nearly all the species of Terebra, enumerated by Lamarck 

 and other authors ; only leaving in the latter genus those species, 

 which being more bulbous, or ventricose, nearly resemble Bucci- 

 num in general form. These last mentioned species, such as 

 Terebra buccinoidea, have been formed into a new genus by 

 Mr. Grray, under the name Bullia. If both these genera were 

 adopted, the genus Terebra would be extinct. PI. xx. fig. 428. 



