292 ME. S. HANLET Olf A NEW VARIETY OP CHAMA. 



On a new Yariety (?) of Ohama, allied to tlie O. arcinella of 

 LinnsBus. By Stlvanus Hanlet, F.L.S. 



[Eead 19th June, 1884.] 



Amon& tlie many novelties added to my collection from tlie shells 

 collected by Admiral Belcher, I descried two specimens which I 

 then supposed to be forms of the "West-Indian Ohama arcinella, 

 Linn. Even now, after long observation, I hardly venture to 

 pronounce them distinct. 



Yet, whether variety or species, they merit notice ; for although 

 the typical form has been frequently and well delineated, I know 

 no other original figure of this abnormal variety (?) since the days 

 of Bonanni, who, in 1684, roughly yet characteristicaRy por- 

 trayed it in his ' Eecreatio mentis ' as from Brazil. It may be 

 designated, then, G. arcinella, var. Bonanni, or 



0. Bonanni. — Testa Gh. arcinellce (Linn.) persimihs, minor 

 auteni quamquam plus ponderosa ; costse radiantes nodoso- 

 dentatse, baud aculeis longis spinosse, pauciores (circiter 8), 

 latiores : intus purpurea. Long. 1 poll. 



Habitat. Brazil ? Zanzibar ? Mus. Hanley. 



Its outline is much blunter and rounder than in the typical 

 form, and its ribs do not exhibit those long spines which form so 

 prominent a feature in that well-known shell. I recognize the 

 long-lost form, so coarsely yet so adequately depicted by Bonanni 

 in his ' Eecreatio ' (f. 336), copied by Lister (Hist. t. 355. lower 

 f. 192) and Petiver (Pterig. pi. 15. f. 389). These figures were 

 not originally cited by Lamarck himself as identical with the 

 Chemnitzian C. arcinella (f. 522-3), but were referred to in the 

 edition by Deshayes. 



The colour of both individuals was externally whitish ; neither 

 of them displayed the yellow interior so frequent in the larger 

 form ; the pustules on the lunule, moreover, seem larger than in 

 the latter, which has usually 12 ribs. 



The smaller of my specimens was attached to a worn valve 

 of an Area, that reminds me in its outline of the Peruvian 

 G. hrevifrons. 



I have lately seen a specimen attached to a Pectunculus 

 ascribed by Eeeve to Zanzibar. 



