March 30, 1906.] 



SCIENCE. 



509 



of reversed motion secured during a lengthy 

 train journey. 



If one admits the accuracy of these observa- 

 tions, they seem to me somewhat to modify 

 the current theoretical explanations of the 

 illusions of reversed motion. Such an asser- 

 tion as that of Bowditch and Hall, for in- 

 stance, that ' it is impossible to conceive how 

 this persistent after-inipressiop of motion can 

 be a product of experience or association,' 

 may, perhaps, be satisfactory so far as their 

 observations go, but does not seem satisfactory 

 when our observations after prolonged stimu- 

 lation are also considered. Still, it may well 

 be, and I think is, true that the illusion 

 we are describing is independent of the illu- 

 sion of reversed motion generally secured. 

 On the other hand, an observation of Exner's, 

 to the effect that an after-image of movement 

 can be engendered by passing the eye over 

 resting objects as well as by the usual method 

 of moving objects past the resting eye, may 

 possibly furnish the cue to the explanation of 

 the matter under discussion, without the as- 

 sumption of an illusion of judgment or of 

 any other ' central ' process. It may be that 

 continued and intent scrutiny of .the perfo- 

 rated drum-paper induced a habit of eye-move- 

 ment in my experimenter, and that the sight 

 of the drum was thereafter a stimulus which 

 innervated unconscious eye-movements, even 

 after the lapse of considerable time-intervals. 

 This hypothesis, however, would appear to 

 necessitate the acceptance of the rather de- 

 batable theory of unconscious eye-movement 

 propounded by Ilelmholtz. 



Guy Montrose Whipple. 

 Cornell University. 



a note on mid-cretaceous geography. 

 In his Berne address, published in the 

 October number of the American Geologist, 

 Professor Osborn refers' to the apparent geo- 

 graphical unity between North and South 

 America during the mid-Cretaceous and con- 

 tinuing possibly to the basal Tertiary. This 

 connection is indicated by the fauna of the 



'Osborn, H' F., Amer. Geol., 36: 213, 100.5. 



Notostylops beds of Patagonia.^ Hauthal, 

 who has done more or less stratigraphical work 

 in the region referred to, published a brief 

 note on some of these formations several years 

 ago,' which is of some interest in this connec- 

 tion because the same observer discovered a 

 plant-bearing layer at one horizon, which 

 yielded a number of forms of great interest, 

 particularly from the view-point of the phyto- 

 geographer. These plants were worked up 

 by Kurtz.* His paper, from the fact that it 

 was not illustrated and because of its place of 

 publication and language, being in Spanish, 

 is not likely to attract the attention of paleon- 

 tologists which it deserves, and is worth re- 

 calling at this time.'^ 



The plants occur at Cerro Guide .in the 

 province of Santa Cruz, in a layer of fine gray 

 sandstone which grades upward into a coarse 

 greenish sandstone, the whole fifty to sixty 

 meters in thickness and overlain by beds con- 

 taining Tertiary fossils. 



The Argentine geologists correlate the lower 

 Notostylops beds containing a rich vertebrate 

 fauna and this plant horizon with the Ceno- 

 raanian. If the determinations are correct, 

 which fact it is difficult to properly estimate, 

 because they are not figured, the plants fur- 

 nish striking- confirmation of this view. 

 There are thirty-one forms described, in- 

 cluding a new species in Abietites, Araucarites 

 and Perseophyllum. Eliminating these from 

 our calculations, we have twenty-eight forms, 

 of which twenty-one, or seventy-five per cent., 

 are characteristic types of the Dakota group 

 flora. It is a significant fact that the meager 



" Ameghino, F., ' Sinoptico de las formaciones 

 sedimentarias, terciarias y cretaceas de la Argen- 

 tina. Anal. Museo Naeional Buenos Aires ' 

 (ill.), 8: 1-12, 1902. 



' Hauthal, R., ' Ueber patagonisches Tertiar, 

 etc.,' Zeitsch. Deutsck. geol Gesell, 50: 436-440, 

 1898. 



'Kurtz, F., 'Contribuciones a la paliEOphytologia 

 Argentina-Sobre la existencia de una Dakota 

 Flora en la Patagonia austro-occidental,' Reinsta 

 Mitseo La Plata, 10: 43-60 (1899), 1902. 



MVilckens, Neites Jahrb. f. Min. Geol. n. 

 Palciont., 21: 98-19.5, October, 1905, gives a quite 

 full historical review and admirably summarizes 

 our present knowledge of Patagonian geology. 



