ON MOLLUSCA OF THE WEST COAST OF NORTH AMERICA. 591 
Plate. Fig. No. 
VI. 54. 49. ?Gratelupia mactropsis, Conr., n.s, ae a punctatostriatus. | 
?Miocene. Isthmus of Darien. Resembles G. Hydeana, Cony. 
Eocene. 
» 55. 50. Meretrix Dariena, Conr., us. (Comp. Cyelina subquadrata.] 
?Miocene. Isthmus of Darien. 
» 03. 51. Tellina Dariena, Conr.,u.s. PMiocene. Isthmus of Darien. 
VU. 57. 52. Natica._Ocoyana, Conr.,n,s. [Marked 51 on plate: err.] Ocoya 
or Posé Creek. 
» 67. 58. Natica geniculata, Conr., n.s. Ocoya Creek. Resembles WN. 
alveata. 
» 62. 54. Bulla jugularis, Conr., u.s. Ocoya Creek. 
» 69. 55. Pleurotoma transmontana, Conr.,n.s. [Marked 60 on plate: err. 
Closely resembles Chrysodomus dirus, Rve.] Ocoya Creek. 
56. Pleurotoma Ocoyana, Conr.,n.s. [Omitted in the text] Qcoya Cr. 
» 72. 57. Syctopus [Ficula.] Ocoyanus, Conr., n.s. Ocoya Creek. 
VU. 73. 58. Turritella Ocoyana, Conr., n.s. Ocoya Creek. 
» 76. 59. Colus arctatus, Conr.,n.s. Ocoya Creek. 
» 15. 60. Tellina Ocoyana, Conr.,n.s. Ocoya Creek. 
» @7. 61, Peeten Nevadanus, Conr.,u.s. Very like N. Humphreysii, Mary- 
land, Miocene. Ocoya Creek. 
TX. 83. 62. Pecten calilliformis, Conr., ns, Very like P. Madisonius, Say, 
Virginia, Miocene. Ocoya Creek. 
The following species are not described in the text, but quoted in the list. 
Vide p. 320 :— 
VIL. ?78. 63. Cardium, sp. ind. Ocoya Creek. 
64, Arca, sp. ind. Ocoya Creek, 
» £80. 65. Solen, sp. ind. Ocoya Creek. 
» 81. 66, Dostnia, sp. ind. Ocoya Creek. 
» ?79. 67. Venus, sp.ind. Ocoya Creek. 
68. Cytherea ?decisa, Conr. Ocoya Creek. 
69. Ostrea, sp. ind. San Fernando. 
70. Pecten, sp.ind. San Fernando. 
71. Turritella biseriata, Conr., ?n.s. San Fernando. 
VII. 758. 72. Trochus,sp.ind. Benicia. 
» ?°09, 73. Turritella, sp.ind. Benicia. 
» (?@1. 74. Buecinum Pinterstriatum. San Pedro. 
* 75. Anodonta Californiensis, Lea. Colorado Desert. 
Mr. Conrad, than whom there is no higher authority for American Tertiary 
fossils, considers the age of the Eocene boulder ascertained; and that “the 
deposits of Santa Barbara and San Pedro represent a recent formation, in 
which (teste Blake) the remains of the Mammoth occur: and the shells indi- 
cate little, if any, change of temperature since their deposition.” But he 
acknowledges that the intermediate beds are of uncertain age. Those on 
Carrizo Creek he refers to the Miocene, some characteristic species being 
either identical with the Eastern Miocene or of closely related forms. In 
addition to the species tabulated in this Report, he quotes, as having been 
collected in California by Dr. Heermann, “ Mercenaria perlaminosa, Conr., 
searcely differmg from M. Ducatelic, Conr.; and a Cemoria, Pandora, and 
Cardita of extinct species, closely analogous to Miocene forms.” The casts 
from Ocoya Creek were too friable to be preserved, and are figured and de- 
scribed from Mr. Blake’s drawings; these also are regarded as Miocene. The 
San Diegan specimens are too imperfect for identification ; they are referred 
to the Miocene by Conrad, but may perhaps be found to belong to a later 
. * Several fossils are figured in plates vii. and viii., to which no reference is made in the 
text. It is unsafe to conjecture the genus to which many of them belong, but it is pre- 
sumed that they relate to the indeterminate species here quoted. 
