464 MAZATLAN UNIVALVES 



Conch. Ic. pi. 1, f. 1. Mice, in Zeit. f. Mai. 1851, p. 23, 



no. 101. C. J5. Ad. Pan. Shells, p. 48, no. 32. 

 Voluta incrassata, Dillw. Descr. Cat. p. 516, no. 35, 1817. 



Wood Ind. Test. pi. 19, f. 3'. 

 Strephona (Dactylus) incrassatus, H. fy A. Ad. Gen. i. 143. 



The few specimens sent of this fine species were soon secured 

 by collectors. They vary in amount of angulation and eleva- 

 tion of spire, and in the pattern of the very characteristic dark 

 blotches. A broad specimen, shoulder flattened and angle 

 developed, measures long. 2 "3, long. spir. '22, lot. 1'18, div. 110. 

 A slender sp. scarcely angulated, long. 2 '45, long. spir. "3, 

 lout. 1-19, div. 100. 



Hob. Peru, Deshayes. Panama, very rare, C. B. Adams.. 

 Gulf Mcoya ; in sandy mud, 9 fm. ; Cuming. Bay of Mag- 

 dalena, Duclos : 24*5 N. [?] Mazatlan ; extremely rare: 

 L'pool fy Havre Coll. 



Tablet 2110 contains the broad sp. 



| 591. OLIVA MELCHEBSI, Mice. 



Zeit.f. Mai. 1851, p. 24, no. 104. 



Oliva angulata, jun. P. P. C. Cat. Prov. 



Comp. Oliva subangulata, Phil. Albild. 



Comp. O. Cumingh, Eve. Conch. Ic. pi. 11, sp. 19, (Gulf of 



California, Capt. Donnel.) 

 Comp. O. polpaster, Duel. G-uer. Mag. Zool. 1839, pi. 20 : 



Rve. Conch.. Ic. pi. 14, f. 29: var. (Bay of Montija, sandy 



mud, 13 fm. Cuming. Panama, Duclos.) 



The Mazatlan shells of the reticularis type divide themselves 

 with tolerable facility into two sets, of which one answers 

 in the main to the description of Menke (too minute however 

 to include the whole group), and the other appears to be the 

 O. venulata of Menke and Prof. Adams. In another collec- 

 tion were found several distinct varieties of the latter. The 

 discrimination of these from each other and from O. reticularis 

 is a matter of extreme difficulty ; which Mr. Reeve escapes by 

 uniting them all together. As the Pacific and Atlantic shells 

 however have a different habit, it seemed right for the present, 

 in so difficult a genus, to keep them apart. 



The shells here grouped are intermediate in character be- 

 tween O. angulata and O. venulata. They are smaller than 

 the former, larger than the latter ; with an acute spire, and an 





