CHAPTER XXX. 



LAMELLIBRANCHIA.* 



Systematic : — 



I. Protobranchia, gills bipectinate, branchial processes plate-like 

 and not reflected, foot with creeping sole. 



Nucula, Yoldia, Solenomya. 



II. Filibranchia, gill-filaments distinct and reflected ; solid 

 interlamellar junctions, cilia forming interfilamentar junctions. 



Area, Mytilus, Modiolaria, etc. 



III. Psbudolamellibranchia, the gill-filaments reflected and 

 loosely connected by ciliated discs or vascular junctions, interlamellar 

 junctions vascular; gills folded and filaments at base of grooves 

 modified. 



Pecten, Ostrea, etc. 



IV. Eulamellibranchia, gill-filaments of plate-like gill con- 

 nected by vascular interfilamentar and interlamellar junctions, re- 

 flected. 



Cardium, Teredo, Gyclas, Unio, Venus and most Lamellibranchs. 



1. Oviposition and Care of the Brood. 



The eggs of the Lamellibranchia may be discharged into the 

 water and there fertilised (Modiolaria and Mytilus edulis, Loven, 

 Barrois, Wilson; Ostrea virginiana, Brooks, No. 16; and pro- 



* We have, chiefly for practical reasons, placed the Lamellibranchia be- 

 fore the Gastropoda, because their larval forms appear to be more primitive, 

 and their further development is usually more simple. The relation of the 

 Lamellibranchia to the other divisions of the Mollusca will be discussed 

 later (Chap. xxx.). In the classification of the Lamellibranchs, we have 

 followed Pelseneer's recent works, but it should be mentioned that Grobben 

 has quite recently adopted a new stand-point in classifying the Lamelli- 

 branchia, and has expressed himself as opposed to the use of the gills as the 

 determining feature in their classification (Beitriige zur Kenntniss des Baues 

 von Cuspidaria (Neaera) cttspidata, etc. Arb. Zool. Inst. Wien. Bd. x. 1892). 



