824 APPENDIX. 
except on the posterior slope, where they are small and not prominent, about five in number. 
Cardinal teeth small, numerous, closely arranged, larger towards the extremities. Inner mar- 
gin profoundly dentate; dorsal area rather wide and marked with about six impressed lines ; 
beaks distant. 
Locality.—Tulare valley? Miocene. 
There is but one valve in the collection, and it has some resemblance to A. arata, Say, of the 
Maryland Miocene. The locality is given by Mr. Blake with a mark of doubt. 
TAPES. 
26. T. DIVERSUM, Sow., Pl. III, fig. 31, 31a and 31 b.—Obtusely cval or suborbiculary ventri- 
cose, inequilateral; disk with numerous radiating prominent strie or ribs, and concentric 
wrinkled lines, which are profound anteriorly; posterior margin nearly direct, obtusely rounded 
or subtruncated ; inner margin with small crenulations ; ligament plate broad and profoundly 
indented. / 
Locality.—San Pedro, in calcareous marl. Recent formation. 
SAXICAVA, Fleur de Bell. 
27. 8. ABRUPTA, Con., Pl. III, fig. 25 and 25a.—Suboval, ventricose, inequilateral ; concen- 
trically wrinkled ; anterior margin obtusely rounded obliquely inwards ; posterior extremity 
truncated, direct, dorsal and basal margin nearly parallel. 
Locality.—San Pedro. Recent formation. 
PETRICOLA, Lam. 
28. P. PEDROANA, Con., Pl. III, fig. 24.—Elliptical, profoundly inequilateral, compressed, 
undulated concentrically, and with very minute closely-arranged radiating lines. 
Locality.—Occurs with the preceding shell. Recent formation. 
One broken valve of this species occurred in the same specimen of rock in which they had 
bored. Some specimens of the Saxicava are entire, and fill the cavities they have formed, when 
living. 
SCHIZOTHCERUS, Conrad 
. 29. 8. NUTTALLI, Con., Pl. IV, fig. 33 and 33a.— Ovate, ventricose, gaping widely posteriorly ; 
moderately thick in substance; anterior side short, abruptly rounded at the extremity ; posterior 
side elongated, extremely truncated ; dorsal line slightly concave ; umbo not prominent ; basal 
margin profoundly rounded ; hinge-plate broad, cartilage pit large, obliquely ovate, profound ; 
cardinal teeth in the left valve two, one in the right valve; anterior cardinal plate broad, with 
an angular depression throughout its entire length, posterior one narrow, with a deep angular 
channel in which is a bifid plate in the right valve; cavity of shell and umbo profound. 
Locality.—San Pedro is calcareous marl. Recent formation. ; 
I have referred this shell to the same genus in which I placed Lutraria Nuttalli of the Cali- 
fornia coast. The hinge is very similar to that of Zutraria, but the long deep channels of the 
hinge are similar to those of L. Nuttalli, the animal of which differs from that of Lutraria. 1 
do not know of any recent species of the latter genus in California. 
LUTRARIA? Lam. 
30. L. TRASKEI, Con., Pl. III, fig. 23.—Suboval, ventricose, inequilateral, hinge and basal 
margin nearly parellel; posterior margin subtruncated and shightly oblique, or approaching 2 
direct outline; posterior extremity rounded. 
