1894 PBOCEEDINGS OF THE NATIONAL MUSEUM. 197 



meters. Sculpture closely resembling- that of A. scahra Nutt.-Rve., 

 which also occurs in the Gulf region. The above is much longer in 

 proportion to breadth, more ovate and flatter than seahra of same size, 

 and the apex is less central than in the latter species. 

 It may prove to be an extreme varietal aspect of scabra. 



ACM^.A PATINA, 10 s c h s c h o 1 1 z . 

 Two juniors. 



These are the young of a common varietal aspect of _prt//>/aand were 

 detected at Santa Margarita Islan d (No. 102523, U. S. N. M.), Albatross 



ACMiEA ASMI, M i <l <l e n d <> r f f . 



Common living'. Ballenas Bay, Albatross. 



The above three sjiecies may be regarded as northern forms and 

 their southerly limit is probably in this vicinity. So too with Lottia 

 gigantea, referred to below. 



The following species of the group may on the other hand be con- 

 sidered as more southerly forms and their northerly limit, in a general 

 way in this region. 



ACM^A PEDICULUS, P h i 1 i p p i . 



One example. Tres Marias (No. 32012, U. S. N. M.). 



ACM^A FASCICULARIS, M e n k e . 

 Several specimens. Tres Marias (No. 32(»<>4, U. S. N. M.); Loreto. 



ACM^.A DISCORS, P h i 1 i p j) i . 



Abundant. Tres Marias (No. 32628, IT. S. N. M.); San Bruno, (labb 



(No. 32645, TT. S. N. M.). 



ACM^.A ATRATA, C a r p e ii t e r . 



Two specimens. 

 I Tres Marias (No. 32649, U. S. N. M.); one adult and one Junior. 

 I Acapulco Dall (No. 59671, TT. S. N. M.); dape St. Lucas (No. 59600, 

 [ U. S. N. M.). . 



LOTTIA GIGANTEA, G r a v.. 



One beach shell. Ballenas Bay, Albatro.sN. 



SCHRRIA MESOLEUCA, Menko. 

 Three specimens. Tres Marias (No. 32064, U. S. N. M.). 



SCURRIA MESOLEUCA, Menko ; vav.?= ACM^.A VESPERTINA, Reove. 



Two examples. 



Tres Marias (No. 32629, TT. S. N. M.); Ventosa Bay, Tehuan tepee 



