ORTHOTETES Fischer de Waldheim (pp. 186 et seq.).

This is fig. 4a of Fischer de Waldheim's Oryctographie (1830 ed., pl. 20), and was repeated in the 1837 edition (pl. 20, fig. 4a). In the first instance the legend was merely Orthotetes, but in the second there was added the statement that it was the interior of the lower valve, the cut above being the flattened hinge plate seen from above. (For the original description of the figures see pp. 186-189 of the present report.) This figure has usually been referred to as representing a dorsal valve, but when taken in connection with the hinge plate, with the descriptions, and with subsequent figures, it is quite evidently a ventral valve.

This was fig. 4b of pl. 20 in both editions of the Oryctographie. In the first edition there was no description relating to it, but in the 1837 edition it was said to be the dorsal canal of the valve shown by 4a (1 of this plate).

This figure does not appear in the 1830 edition of the Oryctographie, but was introduced in the 1837 edition. It was there described as the upper valve of Orthotetes n. g., and constituted fig. 4e of pl. 20. In view of the configuration one can not help believing that this also is a ventral valve, an interpretation which would fit well with Fischer's conception of the genus at that time. He conceived it, in fact, to be a pelecypod related to Pedum. It is probable that he had two ventral valves in mind, rather than two dorsals, or than a dorsal and a ventral, because the latter combination shows too conspicuously the inequivalve character of the shell for Fischer to compare it to Pedum, which is of course one of the Pectinidae, while Pedum has a high area and cartilage pit, not at all like the structure or the configuration of the dorsal valve of Orthotetes, but superficially not dissimilar to the ventral valve. Fischer's description and figures seem to bear out these inferences. This figure and 1b are not reproduced in Fischer's treatise of the year 1850.

ORTHOTETES RADIATES Fischer de Waldheim (pp. 189 et seq.).

This figure was fig. 3 of pl. 10 of Fischer's final discussion of the genus in 1850 (see p. 189 of the present work). This is evidently a better drawing of the original of fig. 1 (4a of the Oryctographie), with which the genus Orthotetes was first illustrated. In this place, for the first time, the generic term is supplied with a specific name. Orthotetes radiatus is, therefore, the species on which the genus was originally based, and it had the internal structures of Waagen's Derbya, probably of his camerate division (see Fischer's descriptions).

This figure was not named or described by Fischer in 1850, but it evidently represents the upper cut of fig. 1 (fig. 4a of pl. 20 in the Oryctographie), and without much question belongs to Orthotetes radiatus.

ORTHOTETES SOCIALIS Fischer de Waldheim (pp. 189 et seq.).

This is a reproduction of the figure used by Fischer in 1850 to illustrate his species Orthotetes socialis (it was there fig. 4 of pl. 10), which from his description apparently belongs to the soptate division of Waagen's Derbya.

This was fig. 1 of pl. 10 of Fischer's work on Orthotetes published in 1850. He gave no name or description for it at that time, but it seems probable that it represents the area and interior of Orthotetes socialis. (See pp. 189 et seq. of the present work for Fischer's text and a discussion of it).

STROPHALOSIA CORNELLIANA Derby (p. 276).

A representative ventral valve from Brazil.

Exterior view, X 2.

Interior view, X 3. On the inside of the shell is shown a peculiar thickening which suggests that of Richthofenia permiona Shumard.

"Coal Measures:" Itaituba, Brazil.

CAPITAN FORMATION, GUADALUPE MOUNTAINS.

STROPHALOSIA CORNELLIANA Derby (p. 276).

A ventral valve from Texas referred to this species.

Exterior, seen from above, X 2.

Capitan formation, hill southwest of Guadalupe Point (station 2906).

LEPTODUS GUADALUPENSIS n. sp. (p. 213).

A ventral valve. The specimen represented by this figure is a mold of the interior, the shell having been more or less completely removed by exfoliation. This is the usual condition in Capitan specimens.

View of the lower side.

Impression of the same, presenting the parts in their natural topographic relations.

Side view, showing how the lateral expansions tend to arch over the interior of the shell.

Capitan formation, Capitan Peak (station 2926).

A portion of the shell showing the papillose or punctate surface. Seen from above, X 2.

Capitan formation, Capitan Peak (station 2926).

LEPTODUS AMERICANUS n. sp. (p. 212).

A young example of this species attached to a branching bryozoan (probably Acanthocladia), showing both valves in conjunction.

Seen from above, X 3.

Seen from below, X 3.

Seen from the side, X 3.

Capitan formation, hill southwest of Guadalupe Point (station 2906).