992 



SCIENCE. 



[N. S. Vol. XXI. No. 548. 



lower Beekinantown to upper Stones River, 

 which interval is repi-esented by several thou- 

 sand feet of calcareous sediments in other 

 regions distant from the shore of that time. 



In marine transgressive overlaps, later 

 members overlap earlier ones toward the 

 source of supply, i. e., towards the old-land. 

 In non-marine progressive overlaps, later 

 members overlap the earlier ones away from 

 the source of supply. Thus in a growing 

 alluvial cone, the later formed beds will extend 

 farther out on to the plain away from the 

 mountain. If several successive fans of this 

 type are formed one above the other, owing 

 to successive elevations of the source of sup- 

 ply, only the latest beds of each delta will be 

 found on the outer edge of this compound 

 delta, the hiatus between the beds being fur- 

 ther emphasized by the erosion which the last 

 bed of the first delta underwent during the 

 time that the early beds of the second delta 

 were deposited nearer the source of supply, i. e., 

 before the last bed of the second delta covered 

 up the remnant of the last bed of the first 

 delta and thi:is protected it from further ero- 

 sion. A good example of this type of overlap 

 appears to be presented by the Pocono, Mauch 

 Chunk and Pottsville beds of the Appalachian 

 region. These formations are with exception 

 of the negligible Greenbrier member, of non- 

 marine origin, representing the wash from the 

 growing Appalachians. In western Pennsyl- 

 vania only the latest beds of each (barring 

 portions removed by erosion between the dep- 

 osition of the successive fans) are found rest- 

 ing one upon the other, the interval between 

 the beds becoming less and less toward the 

 anthracite regions. A. W. Grabau, 



Secretary. 



SECTION OF BIOLOGY. 



At the April meeting Professor H. F. Os- 

 born presented a discussion of 'The Ideas and 

 Terms of Modern Philosophical Anatomy,' and 

 Dr. O. R. Hay described 'Turtles of the 

 Bridger Basin.' The full abstract of Professor 

 Osborn's paper was published in Science 

 for June 23. Dr. Hay gave a brief descrip- 

 tion of the extent of the Bridger beds and of 

 the nature of the materials composing them. 



He expressed the conviction that these deposits 

 had not been made in a lake, but over the 

 flood-grounds of rivers. The region was 

 probably covered with forests, and teemed with 

 animal life. In the streams were numerous 

 turtles. Many species of these have been de- 

 scribed by Dr. Leidy and Professor Cope. In 

 the speaker's hands are materials for the de- 

 scription of about a dozen more species. The 

 American Museum party of 1903 collected 

 many specimens of the genus and these have 

 furnished good skulls, neck, shoulder and pel- 

 vic girdles, and the limbs. These materials 

 confirm the validity of Lydekker's group called 

 Amphichelydia, and show that from it sprang 

 the modern super-families Cryptodira and 

 Pleurodira. 



At the May meeting of the section papers 

 were presented by Professor E. B. Wilson on 

 ' Observations on the Chromosomes in Hemip- 

 tera,' and by Professor H. E. Crampton on 

 ' Correlation and Selection.' 



Professor Wilson's paper presented the re- 

 sults of an examination of the mode of distri- 

 bution of the chromosomes to the spermatozoa 

 in Lygceus turcicus, Ccenus delius, Podisus 

 spi7iosus and two species of Euchistus. In 

 none of these forms is an accessory chromo- 

 some (in the ordinary sense) present, all of the 

 spermatozoa receiving the same number of 

 chromosomes, which is one half the sperma- 

 togonial number (the latter number is in 

 Podisus sixteen, in the other forms fourteen). 

 In all these forms, however, an asymmetry of 

 distribution occurs such that two classes of 

 spermatozoa are formed in equal numbers, both 

 receiving a ring of six chromosomes (in 

 Podisus seven) that are duplicated in all the 

 spermatozoa, and in addition a central one 

 which in one half the spermatozoa is much 

 smaller than in the other half. These cor- 

 responding but unequal chromosomes (which 

 evidently correspond to some of the forms 

 described by Montgomery as ' chromatin 

 nucleoli,' and agree in mode of distribution 

 with that which this author has described in 

 the case of Euchistus tristigmus) may be called 

 the ' idiochromosomes.' They always remain 

 separate in the first division, which accord- 



