ON MOLLUSCA OF THS WEST COAST OF NORTH AMERICA. 349 



Been no marks by which it can be separated from S. australis, though he 

 expects that some will be eliminated hereafter. 



76. The Upper Californian district presents a very peculiar assemblage 

 of shells ; essentially of a temperate cast, but including a few forms of tropical 

 type. The leading species are as follow, including several which also make 

 their way into Oregon and Lower California : — 



Discina Evansii. 



Pholadidea penita, 



Parapholas Californica. 



Petricola Californica. 



Rupellaria lamellifera. 



Saxidomus Petitii and Nuttalli. 



Platyodon cancellatus. 



Cryptodon Nuttalli. 



Sphsenia Californica. 



Thracia curta. 



Mytilimeria Nuttalli. 



Pandora punctata. 



Machsera Nuttalli. 



Solecurtus subteres and Califomicus. 



Sanguinolaria grandis. 



Tellina Bodegensis, secta and alta. 



Donax flexuosus and Califomicus. 



Mactra Californica and planulata. 



Trigona crassatelloides. 



Dosinia callosa. 



Venus Nuttalli. 



Tapes straminea. 



Trapezium Californicum. 



Cbama exogyra. 



Diplodonta orbella. 



Kellia Laperousii. 



Mytilus Cabfornianus and bifurcatus. 



Modiola recta and nitens. 



Nucula ccelata. 



Leda polita. 



Isognomon costellatus. 



Pecten latiauratus. 



The total number of mollusks known to inhabit this district, excluding most 

 of those of which the habitat is only loosely stated as " California," &c., is as 

 follows: — Bryozoa, 1 ; Palliobranchs,2; Lamellibranchs, 73; Ordinary Gaste- 

 ropoda, 100; Toxifera, 2; Proboscidifera, 24: Total, 202. Of these there have 

 only as yet been found common also to Lower California (San Diego to Cape 

 St. Lucas), Bryozoa, ; Palliobranchs, ; Lamellibranchs, 27 ; Ordinary 

 Gasteropoda, 23 ; Toxifera, 0; Proboscidifera, 6 : Total, 56; but as scarcely 

 140 species are as yet known from that region, it is next to certain that the 

 common species will be hereafter found much more numerous. Of the compara- 

 tively small assemblage known from Upper California, containing next to no 

 pelagic forms and only about half-a-dozen minute species, it will be observed 

 how large a proportion are bivalves, and how few proboscideans ; also how 

 much larger the proportion of the' widely extended species is in the former 

 than in the latter group. A very few, as Cultellus lucidus and Lyonsia 

 Californica, are perhaps identical with North Atlantic shells ; but in general 

 there is a wide disagreement. Here are found the largest species oi Parapholas 

 and Trigona; and the types of Platyodon, Cryptodon, Mytilimeria and 



Bulla nebulosa. 



Tornatina culcitella and cerealis. 



Lepidochiton Mertensii and scrobiculata. 



Mopalia Simpsonii. 



Chitonida? NuttaUi, ornatus, Monte- 



reyensis, Hartwegii. 

 Nacella depicta and incessa. 

 Acmsea scabra and toreuma. 

 Fissurella ornata and volcano. 

 Lucapina crenulata. 

 Haliotis, 5 sp. 

 Trochus filosus. 

 Ompbalius aureotinctus. 

 Trochiscus Norrisii. 

 Crepidula rugosa. 

 Aletes squamigerus. 

 Litorina planaxis. 

 Trivia Californica. 

 Defrancia bella. 

 Conus ravus. 

 Odostomia gravida. 

 Cbemnitzia tenuicula and torquata. 

 Neverita Recluziana. 

 Mitra maura. 

 Marginalia Jewetii. 

 Purpura macrostoma and harpa. 

 Monoceros engonata and lapilloides. 

 Nitidella Gouldii. 



Columbella carinata and StaBarbarensis, 

 Nassa perpingius. 

 Cerastoma Nuttalli. 



