The work on the interesting silicified Miocene insects found imbedded in nodules, in lake bed strata, in California mountain areas, which must be recovered by acid extraction, is of necessity very slow and painstaking (see Pierce, various dates). At present I have mounted 7,019 balsam slides of extracted material derived from 2,441 nodules, although a total of 32,898 nodules have been accessioned. Every nodule holds the potential of something new and interesting. The reporting on the findings must be by individual groupings of eggs, larvae, pupae, and adults—as time to work them up is available. In a group like the blood sucking midges of the family Ceratopogonidae (formerly reported as Heleidae, recently ruled out by the International Commission on Nomenclature), the eggs offer a special problem, for only a few living species are recorded and described. I should state that prior to the early papers in this series, fossil insect eggs were unknown. A total of 38 Dasyhelea eggs have been isolated. The larvae, having never been correlated with pupae and adults systematically, are a distinct problem. A total of 80 dipterous larvae are at hand, but not yet separated to family. Our wealth lies in 818 dipterous pupae belonging to the Ceratopogonidae (Heleidae), and Chironomidae (Tendipedidae). On these I will begin to report in this article. There are 60 fossil adults yet to be studied and separated to family, and there are some chances of correlation to the pupae. In nine cases, the adults within the pupa, with abdomen still extended, are being studied. In no series of fossil insects have all stages of the insects been recovered in such perfect three-dimensional condition, crystal clear, and often manifesting internal organs: intestines, nervous system, brain, and tracheal system. This material may become a foundation stone in paleoembryology, using the term in its broad sense as deW D W I G H T P I E R C E

In No. 22 of this series (Bull. So. Calif. Acad. Sci. 58:72-78, 1959), the writer presented a general report on studies of fossils found in calcareous petroliferous nodules of Miocene age in Southern California. Recovery of the fossils has continued, with particular concentration on the nodules from the Calico Mountains. The vast amount of material accumulating, both in the Los Angeles County Museum laboratory, and in that of Mrs. Ruth Kirkby, at her home in Riverside, California, necessitates breaking down the results in short papers as rapidly as accurate reports can be prepared. The present paper includes some of the rarer finds in several orders: Collembola, Ephemerida, Plecoptera, Corrodentia, and Coleoptera.