Abstract

1. Leperditia Hicksii, Jones. Pl. V. fig. 16 (reversed and imperfect).

Small, ovate; hinge-line short; posterior margin broadly curved, anteriorly rather narrower. Ocular spot indicated by a subovate, smooth, and faintly depressed area, reaching up to the hinge-line. Muscle-spot marked (on one side) by a faint irregular subcentral depression, whence a branching vein-like line of bright pyrites runs downwards nearly to the ventral border. Surface mostly punctate by the exposed cellular structure of the test, which as been converted into iron-pyrites, and nearly bared of its outermost layer.

This is the smallest Lperditia I know, and differs from others chiefly in its very nearly oval outline, and in the relative largeness of its eye-spot.

The still smaller Primitia solvensis was at first classed as a Leperditia, but has been subsequently referred to a more appropriate genus.

The above-described old Cambrian Leperditia is here named after its discoverer.

2. Entomis buprestis. Pl. V. fig. 15.

Leperditia bupestris, Salter, Brit. Assoc. Rep. 1865, Trans. Sect. p. 285.

L. punctatissima, Salter, Siluria, 1865, Appendix. p. 519.

This is nearest to Entomis divisa, Jones (Monthly Microsc. Journ. Oct. 1870, pl. lxi. fig. 12), but differs from it chiefly in the furrow being nearly vertical across each valve, instead of following a curve. The furrow on the specimen is defined, though faintly, on one of the valves, and its is marked by symmetrical fracture on each*. The beauty of the pitted pyritous valves is striking, but not uncommon, especially in Carboniferous bivalved Entomostraca. The shape