78 PATELLIDyE. 



Dr. Paul Fischer's classification (Manuel de Conch., p. 866, 1885) 

 is as follows : 

 Genus PATELLA. 



Subtgenus Patella s. s. Brachial cordon complete ; no tuber- 

 cles on the epipodial line ; dentition 3(i 202 i) 3 . P. vulgata, etc. 

 Section Ancistromesus Dall. P. mexicana. 

 Section Olana Ads. P. cochlear. 

 Section Scutellastra Ads. P. pentagona. 

 Section Cymbula Ads. P. compressa. 

 Section Patellastra Monts. P. lusitanica. 

 Subgenus Patinella Dall. Branchial cordon complete ; epipo- 

 dial line scalloped ; no central tooth ; dentition 3 ( 2 101 2)3. P 

 magellanica. 



Subgenus Nacella Schum. Animal as in the last. Shell 

 oval, thin, pellucid, summit anterior, submarginal. N. 

 mytilina. 



Section ? Cellana Ad. 



Subgenus Helcion Montf. Branchial cordon interrupted in 

 front. Epipodial line papillose; dentition 3 (i 202 i) 3 . H. 

 pectinatus. Synonym Patina (Leach) Gray. P. pellucida. 

 Subgenus Helcioniscus Dall. Branchial cordon interrupted ; 

 sides of the foot smooth ; dentition 3 (< 2 lo \~)z. H. variegatus. 

 Genus TRYBLIDIUM Lindstr., 1880. Shell like Patella; muscle- 

 scar broken into a number of separate impressions (fossil.) 



Subgenus Palceacmcea Hall, 1873. Shell like Scurria; 



muscle-scar like Tryblidium (fossil.) 



Dr. Fischer places Metoptoma in Capulidce on account of the pos- 

 terior apex, which is unlike all docoglossate limpets. 



It is evident that a great mass of material must be examined 

 before a just appreciation of the constancy of the characters used to 

 separate groups in this family can be attained. 



A survey of all available sources of information upon the soft 

 parts and radulaB has convinced me, against my preconceived ideas, 

 that the presence or absence of a rhachidian tooth and the continuity 

 or interruption of the branchial cordon are not sufficiently constant 

 to be used as characters for the separation of genera. In some cases 

 it is evident that they are scarcely specific. The radulse should be 

 thoroughly re-examined, as many of the published figures are not 

 sufficiently accurate to be of much use. 



