168 SHELLS OF LOWER CALIFORNIA— STEARNS. 



the variety palmata,* of which six examples now before me display 

 from 24 coarse ribs in the largest specimen 1.03 inch in length to only 

 113 ribs in the smallest which measures only .47 of an inch in length; 

 the exceeding prominence of the ribs in this specimen, projecting 

 greatly beyond the margin, give the edge a digitated appearance, 

 suggesting in miniature some of tlie Indo-Paciflc limpets; for illustra- 

 tion Patella saccharina Linn»us. 



The various aspects presented by lecanium in its numerous varieties 

 and intermediate forms are such, that to quote Carpenter,! " 1 have 

 found it impossible to separate them," hence my inclusion of his wquUi- 

 rata in the synonymy herein given. 



If, as Carpenter says,| ">S'. maura Sby.. is one of the varieties of this 

 species," and '■'■ 8. ferrugineaUye., is jjrobably described from the inter- 

 mediate forms" between 8. maura and 8. p((lviata, then these should be 

 added to the synonymy. Carpenter regarded the form wquilirata as a 

 Lower Californian rather than a Gulf species.§ He credits it to the 

 northerly stations of Cerros Island (Ayres and Veatch's collections), 

 also to Margarita Bay (Pease shells) where he gives " leviuscula Sby., 

 teste Cuming," as a synonym of it, and he also reports it as from Cape 

 St. Lucas in the Xautus collection. 



, The Ayres, Veatch, Pease shells may be regarded as inhabiting 

 exterior or ocean stations, being the outer or western coast of the penin- 

 sula, while the latter place, Cape' St. Lucas as well as the Tres Marias, 

 where both the typical lecanium and wquilirata variety are found, may 

 be regarded geographically as well as biologically as intermediate 

 middle or common ground, hence the occurrence or presence of both of 

 these forms; or, again, if the jequilirate form should be by some persons 

 viewed as an extra limital aspect of leeaniiim, then perhaps we should 

 include in the group as varieties and therefore synonyms of the southern 

 8. costata, a rather small, delicate, closely ribbed a?quilirate shell, the 

 ribs fine rather than coarse; this form is reported from Guacomayo 

 (Cuming) Sowerby, and Panama (C. B. Adams); also in the Stearns 

 collection from Panama (Bridges), and Valparaiso (Brannan); Dr. Jones 

 obtained specimens at Payta. Some of the examples of costata, the 

 more coarsely ribbed specimens, are so close to the selected delicate 

 examples of miulUrata from the Tres Marias as to make it difficnlt if 

 not impossible to satisfactorily segregate the two, were they mingled 

 without previous marking, many individuals of each run so closely 

 together. The southern 8. costata is, aside from its inferior size and 

 more delicate sculpture and structure, more helcion-shaped, with the 

 apex more or less recurved and nearer the margin. 



* S. lecanium, with variety palmata, was plentiful at Cape St. Lucas. (Xantus Col- 

 lection.) B. A. Eeport 1863, p. 621. 

 + Maz. Cat., p. 182. 

 t Brit. Assn. Rejit., 1863, p. 545. 

 $ B. A. Report, 1863, p. 626. Id. 6(34, 666, and 676. 



