KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 48. N:0 1, 



9 



Prosobranchia. 



Heart loith the auricle before the ve?itricle; respiratory organ a cteyiidvum in jront 

 of the heart {seldom secondary hranchice or none); nervovs system of the strefionfAirous 

 type; animal nearly always gonochoristic. 



Subordo 1 Diotocardia (Aspidobranchia). 



Heart with one (Docoglossa) or two (Rhipidoglossa) auricles; ctenidium bipin- 

 nate ; pedal ganglia not developed, replaced by longitudinal ganglions cords with 

 transverse commissures. Shell never siphonated. 



Synopsis of Families. 

 A. Docoglossa. 



Radula with 1 — 3 lateral teeth; heart on the left side of the body, before the 

 rectum, with I auricle ; no epipodium. Shell limpet shaped without internal callus 

 and without slits; apex straight conic or inclined forward, never backward. 



1. A real ctenidium in the mantle cavity on the left side of the body; no accessory 

 branchise. Radula without rhachian tooth, of the fornnila 1 . 2 . (1 . . 1) . 2 . 1 or 

 0.2. (1.0.1). 2.0 Fam. A cmcBidm. 



2. No ctenidium in the mantle cavity; accessory branchise in the mantle furrow all 

 around the foot. Radula usually without rhachian tooth; normal formula 3.1. 

 (2. 0.2). 1.3 Fam. Patellida;. 



3. No ctenidium nor accessory branchiae. Radula with a rliachian tooth, of the 

 formula 2.0.1.0.2 Fanu Lepetidce. 



B. Rhipidoglossa. 



Radula usually with many laterals; heart in the median line of the body, 

 pierced by the rectum, with 2 auricles ; epipodium mostly present. Shell usually 

 spirally twisted or, if limpet shaped, with posterior apex. 



K, Sv. Vet. Akiid. Haiidl. Band 48. N;o 1. 2 



