256 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



curve with concavity towards the right anterior corner of 

 the visceral mass. 



(•2) The intestinal coil (Int. 2) placed on the dorsal 

 surface of the visceral mass- Its position varies in different 

 forms, being often much further to the left than it is in the 

 limpet- 



(8) The presence of three uncini and nearly always, at 

 any rate, three lateral teeth on each side of each row of teetli 

 in the radula. 



(4) The strong odontophore with its squarish front, its 

 highly differentiated transverse muscles, and its numerous 

 cartilages (more than the usual two pairs). 



(5) The large development of buccal glandular tissue. 



(6) The pseudo-chamber (or aortic bulb) formed by the 

 varying amount of swelling of the basis of the aorta and 

 posterior artery- 



(7) The practically transverse posterior boundary of the 

 triangular pericardium. 



(8) The absence of a ctenidium, the smallness of the 

 branchial (nuchal) cavity, and the occurrence of a circle of 

 pallial gills. This circle is incomplete above the head in 

 some Cyclobranchs (Helcion), and in others the gills in that 

 position are small (Nacclla). 



(9) The presence of a lateral or epipodial streak. It has 

 not been found in Helcion and its allies, and it disappears 

 in the adult Patella, but persists throughout life in Nacella. 

 It is not known in any of the more primitive Docoglossa 

 (Monobranchs and Lepetidae). 



(10) The specially degenerate eye. 



(11) The numerous differentiated large and small pallial 

 tentacles. 



The following features characterise the whole group of 

 the Docoglossa : - 



(12) The apex of the simple conical shell is typically bent 



