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196 SHELLS OF SAN PEDRO BAY—WILLIAMSON. 
Family AURICULID.. 
Genus MELAMPUS Montfort. 
Melampus olivaceus Cpr. 
Plentiful in mud-flats. 
Genus PEDIPES Blainville. 
Pedipes unisulcatus J. G. Cp. 
Washed ashore in the drift. 
Family SIPHONARITD. 
Genus SIPHONARIA Sby. 
Subgenus WILLIAMIA Monterosato. 
Siphonaria (Williamia) peltoides Cpr. 
One worn shell found in the bay. (C. T.S.) 
Family GADINIID 4. 
Genus GADINIA Gray. 
Gadinia reticulata Sby. 
A single dead shell reported. 
Family MOPALITD®. 
Genus MOPALIA Gray. 
Mopalia ciliata Sby. 
Not rare on rocks. 
Mopalia lignosa Gld. 
Rarer than M. ciliata. 
Family ACANTHOPLEURIDA. 
Genus NUTTALLINA Cpr. 
Nuttallina scabra Rve. 
The most plentiful form of Chiton. 
Family ISCHNOCHITONID.%. 
Genus CHA|TOPLEURA Shuttleworth. 
Cheetopleura (Maugerella) conspicua Cpr. 
Between ledges of rock at Point Fermin, also at White’s Point. 
Lately identified by Dr. R. E. C. Stearns. This species has been dis- 
tributed under the name of Stenoradsia Magdalenensis. 
Cheetopleura Hartwegii Cpr. 
On rocks; not plentiful. 
