PEOCEEDINGS OF UXITED STATES NATIONAL MUSEUM. 413 

 A. Without a cordon. 

 A. Muzzle with lappets. 

 a. Blind. 



Fecf/inodonta Dull. ,, ,, -— - ( ? 



(1-1) V 0{3-3) 

 h. With eyes. 

 Scutellina Gray. Typical species not yet examined. 

 Acm<eaB,ch. _^_^. 



B. Without muzzle lappets. 

 ColUse^Ia Ball, s. s. ^^^^^ 

 ColliselUna Ball. 2 Y2^l.l_2T2• 

 B. With an interrupted cordon ; no lappets, 

 io^m (Gray) Cpr. ^,2-hU2)~i' 



Collisella 



) 

 C. With complete cordon ; no lappets. 



Scurria Gray ( n ot C i^r. ) . -, ^-- - — -— ^ . 

 ' ^ ^1 (2-1-1-2) 1 



Family PATELLID^. 



Without a cervical branchia, but with a more or less complete cordon; 

 muzzle papillose, not frilled, margiiuited, or with lappets. 



A. Branchial cordon complete. 



a. With rhachidian tooth ; branchial lamelljv arborescent, produced ; 

 sides of foot smooth. Anci.'^tromcsus. 



Ancistromesus Ball. 



3 (1-2-2-1) 3 



b. Without rhachidian tooth ; branchial lamelhe short, liuguiform. 



Patella. 



Patella Linn6. Foot smooth, branchial lamellae subequal all around. 

 

 3 (1-2-2-1) 3* 



