1870.] 53 [Dall. 



2. Patinella 1 Dall, n. subg. First inner lateral on each side an- 



terior to the other two. Second laterals largest, denticu- 

 late. Foot with a scalloped frill, interrupted only in front. 

 Branchias as in Patella. 



Formula, 3(2 _ ] ° 1 _ 2)3 - 



Type Patinella magellanica Gmel. (as Patella) Syst. Nat. i, p. 

 3703,no.52. 1792. 



3. Nacella Schum., 1817. Shell thin, pellucid, apex anterior. 



Foot frilled, as in Patinella. Teeth bidentate, arranged as 

 in the last. Branchial lamellse very small in front, but not 

 interrupted. 







Formula, V7i 1.1 2\q" 



Type Nacella mytilina Gmel., Syst., Nat., vol. 1, p. 3698, no. 

 28, 1792 (as Patella) =» Nacella mytiloides Schum., 1817, 

 and Patella cymbularia Lam., 1819. 



B. Branchial cordon interrupted in front. lielcion. 



1. Helcion Montf, 1810. Shell solid, capuloid, with pectinated 



ribs. Teeth? 

 Type Helcion pectinatus (as Patella pectinata) Lin., Gmel., 

 Syst. Nat., p. 3710, no. 93. 1792. 



2. Helcioniseus 2 Dall, n. subg. prov. Shell depressed, solid, 



with a subcentral apex. Teeth arranged as in Patinella. 

 Sides of foot smooth. 



Formula, 8 (2 _ £ _ 2) 8 - 



Type Helcioniseus rota (Chemn.) Eve. (as Patella) Conch. 

 Icon. pi. xvii, fig. 39, a, b, c. 



3. Patina (Leach) Gray, 1840. Shell very thin, pellucid. Sides 



of foot smooth. Third pair of laterals posterior, largest, 

 denticulated. 



Formula, 8 (1 . a , g . 1 y s - 



Type Patina pellucida Lin,, Syst. Nat., xn, 1260, no. 770 (as 

 Patella). 1767. 



1 From patina, a dish. 2 Diminutive of Helcion. 



