Vol. XI] 



BERRY— FOSSIL CHITONS 



445 



Recorded Range: 



Pleistocene: Formation doubtful — Deaclman Island, San 

 Pedro, California (Chace, !). 



Living: Forrester Island, Alaska, (!) to Ventura 

 County, California ( !) ; usually between tides, but recorded to 

 30 fathoms. Also recorded from Laguna Beach, Orange 

 County, California (Guernesey), and San Diego, California 

 (Kelsey). 



Material Exam ined . 



Remarks: One of the two specimens here referred to M. 

 hindsii is that previously reported from the San Pedro Forma- 

 tion by Chace. While I am unable to place it elsewhere, it 

 nevertheless does not seem to be entirely characteristic for this 

 species. In this specimen even the central areas have a beau- 

 tiful basket-like, interwoven appearance to the sculpturing, 

 something like that of the lateral areas but finer. It has been 

 found hopeless to depict this with any real faithfulness in a 

 stipple drawing, but perhaps the illustration will give a hint of 

 what is meant. In all recent specimens I have examined, as 

 well as in the fossil from the Arnold collection, the longi- 

 tudinal sculpture of the central areas is much more marked 

 and results in an effect of fine, rather wavy fluting, instead of 

 interweaving. The divergent riblets on the jugal area of the 

 second valve are generally quite well marked. On the other 

 valves this is less evident. 



Well preserved specimens are readily distinguished from all 

 forms of M. mnscosa by the peculiar cloth-like sculpturing, and 

 the usually flatter outline. In living specimens the girdle char- 

 acters of the two species are widely different. 



