MUREX. Panama Shells. 123 



figure of M. ambiguus. So far, therefore, as we can judge from 

 the 100 specimens collected in one locality, the M. arnbiguus 

 appears to be, not a dominant type, but the extreme limit of 

 variation. It is quite possible, however, that a greater number 

 of specimens collected in various localities would confirm the 

 opinions of Mr. Eeeve. 



Dr. Menke, in distinguishing M. ambiguus from M. nigritiis, 

 among the shells from Mazatlan, (Zeitschr. fur Malak. 1850, 

 p. 188,) finds nine varices in his specimens of the former. 

 M. radix is not mentioned as occurring among them. 



Station. On mud banks at low water ; Cuming : Reeve. 



Our specimens were found in part in the crevices of rocks, 

 but chiefly about stones, where there was more or less of sandy 

 mud, near low water mark. 



Halitat. East Indian Seas ; Dillwyn. 



Shores of Acapulco ; Humboldt and Bonpland ! La- 

 marck : also Valenciennes. 

 Acapulco ; Say in Catal. Mus. 

 Shores of Acapulco and of Panama ; Kiener. 

 Bay of Caraccas ; Cuming ! Sowerby : also Reeve. 

 Bay of Caraccas ; Jay. 

 Panama ; C. B. A. ! 



We collected 100 specimens on the reef. Two of them weigh 

 22 ounces each, and one of these is 53 inches long. 



Habitat of M. ambiguus. Unknown ; Reeve. 



Mazatlan ; Melchers ! Menke. 

 Panama ; C. B. A. ! 

 Murex nigritus Phil, we were unable to find at Panama. 



139. Murex rectirostris. 



Synonymy. 



Murex rectirostris Sowb. in Proc. Zool. Soc. Lond. p. 138. Nov. 1840. 

 Sowb. Conch. 111. pi. 197. f. 111. 1841. 



Reeve Conch. Icon. pi. 22. f. 91. June 1845. 



