TITLES AND ABSTRACTS OF PAPERS 149 



there seems to be no valid evidence for such an assumption. If, as seems 

 likely, some of the endocones are formed before the camerate condition ap- 

 pears, then we have a young shell characterized by an external wall at first, 

 no doubt, conchiolinous, but later more or less calcified, and an internal series 

 of more or less crowded conical partitions, the "endocones" penetrated by a 

 median opening more or less slitlike, but subsequently modified, as shown by 

 Ruedemann, into a central tube, the endosiphuncle. From this we are justified 

 in arguing that the ancestors of these forms had essentially this structure, 

 and this seems to be presented by Volborthella, so far as we know that form. 

 Even should it prove that the septa of this form are without median opening 

 (though the American material, poorly preserved as it is, seems to indicate 

 such an opening), this would not seem to be a valid argument against the 

 acceptance of Volborthella as ancestral — it would merely indicate that the 

 siphuncular tube is a later development. When the camerge first appear on 

 one side, the original outer wall becomes divided, part continuing for a time 

 as the endosipholining, which later ceases to develop, and part continuing as 

 the external shell of the camerated portion. That the camerce are a new fea- 

 ture seems to be clearly indicated by the ontogeny. They indicate a lateral 

 contraction of the visceral sac and a complete cutting off of the space thus 

 produced, whereas the septa of the Orthochoanites represent a withdrawal of 

 the entire animal (except the siphonal tube) and a cutting off of the space by 

 a transverse septum formed at the base of the visceral sac. They are essen- 

 tially homologous to the new formed lateral camerse in the living chamber of 

 Ascoceras, the normal camerate portion of which is of the Orthoceran type 

 except for the addition of collars in the ephebic portion. By acceleration in 

 subsequent forms the marginal camerse appear earlier and earlier until they 

 appear before the endocones, and so more or less completely inclose the endo- 

 conic portion of the shell. 



The derivation of the Orthoceran type of septuun and siphuncle from the 

 Volborthella type, whether that has septal openings or not, seems a very simple 

 matter. Future discoveries in the formations above the Cambric should show 

 the steps in this modification. 



Professor Schuchert agreed with the speaker that Bactrites represented an 

 independent line of development, but doubted its ancestral relationship to the 

 Belemnitidse. 



A second paper by the same author was also discussed in considerable 

 detail by many of the members present. 



INCLUSION OF THE PLEISTOCENIC PERIOD IN THE PSYCHOZOIC ERA 

 BY AMADEUS W. GRABAU 



(Ahstract) 



The author has for many years restricted the term Cenozoic to the Tertiary 

 and used Le Conte's term Psychozoic for the Pleistocenic and the Recent or 

 Holocenic periods, thus making it equivalent to Quaternary in the broader 

 sense. The justification for this appears in the now well established fact that 

 man, the leading index fossil of the Psychozoic, appears in the middle and 

 later Pleistocenic of Europe, while the Trinil race of Java appears to go back 



