532 MAZATLAN BIVALVES 



minente ; nitente, sed striulis tenuissimis, et concentricis, et 

 radiantibus ; valvd alterd dent. card. post, elongato, ant. evanes- 

 cente, lat. nullis ; alterd 



One fresh, minute, and nearly perfect valve was found, which 

 is described because of its abnormal dentition. The texture, 

 as seen in the microscope, closely resembles chalcedony. The 

 nuclear umbo is whitish. Long. '02, lat. "028, alt. '006. 



Hob. Mazatlan ; 1 valve off frond of Murex nigritus : IS pool 

 Col. 



Tablet 2529 contains the specimen. 



[FAMILY AECAim] 



689. AECA , sp. ind. (b.) 



Tablet 2524 contains a minute valve, "048 by '03, swollen, 

 with about 20 very fine rounded nodulous ribs, with the broad 

 interstices strongly decussated. 



Hob Mazatlan : 1 valve on Spondylus ; L'poot Col. 



[FAMILY PECTINID^E.] 



690. PECTEN , sp. ind. (a.) 



Tablet 2525 contains 2 minute valves, broad with large ears, 

 whitish, spotted with olive brown. The youngest, '05 across, 

 is capped at the apex with a Lima-shaped body, and this again 

 with the minute oval nucleus, about '004 across. The shape 

 and sculpture resemble Margaritiphora, the ribs being scarcely 

 developed, and the cellular layer conspicuous. 



ffab. Mazatlan ; 4 young fresh valves, off Spondylus ; 

 L'pool Col. 



691. PECTEN , sp. ind. (b.) 



Tablet 2526 contains a fragment of a pink shell, apparentlj 

 shaped like P. varius. 



