ENTELETES sp. c (p. 297).

A small ventral valve referred to this species.

Exterior.

Side view in outline.

Interior, X 3.

Delaware Mountain formation, Diablo Mountains (station 3764).

Dorsal valve of figs. 1 to 1b.

Exterior.

Side view in outline.

Interior, showing dental plates, cardinal process, etc., X 3.

Delaware Mountain formation, Diablo Mountains (Station 3764).

ENTELETES ANGULATUS n. sp. (p. 295).

A somewhat incomplete ventral valve. An imperfection on the umbo discloses the closely arranged septum and dental plates.

Seen from above.

Side view in outline.

Hueco formation, Diablo Mountains (station 3764).

ENTELETES DUMBLEI n. sp. (p. 295).

An imperfect but well-preserved example showing both valves in position.

Posterior view. The specimen was here posed so that the ventral valve was below.

Ventral view.

Side view in outline.

Hueco formation, Diablo Mountains (station 3764).

DERBYA? CRENULATA n. sp. (p. 183).

A well-preserved specimen retaining both valves in position.

Dorsal view.

Ventral view.

Posterior view.

Surface, X 5.

Side view in outline.

Delaware Mountain formation, Diablo Mountains (station 3764).

DERBYA NASUTA n. sp. (p. 182).

An imperfect specimen with both valves in position.

Posterior view.

Side view.

Ventral view.

View of the interior from the front backward. Above is the ventral valve with its median septum; below, the dorsal valve with its hinge plate and cardinal process. The cardinal process is deeply divided, the septum of the ventral valve passing between the two forks. The cardinal process in this case is a little asymmetrical, and this feature is enhanced in the drawing by the view being taken slightly to one side. Upon the left the tooth and socket are shown, partly concealed by portions of the hinge plate which project before and above them.

Delaware Mountain formation, Diablo Mountains (station 3764).