534 



SCIENCE 



[N. S. Vol. XXVIII. No. 720 



ence along the southern border of the deepen- 

 ing Ontario Valley. This southern border, 

 partly shown in the Niagara escarpment, 

 must be regarded as the inface of a revived 

 cuesta, of which the Ontario Valley is the 

 inner lowland. Examples of ohsequent 

 streams flowing down the inface of the cuesta, 

 and cutting backward from it, are found in 

 the old Saint David's gorge, which had cut 

 back as far as the present Whirlpool; in 

 Irondequoit Bay, often regarded as the former 

 path of the Genesee, but clearly deepened be- 

 yond any depth reached by the Genesee or 

 Canaseraga; and probably Sodus Bay. East- 

 ward the Ontario Valley becomes narrower 

 though the flooded portion is wide. The On- 

 tario River headed eastward, probably passing 

 through Oneida Lake from Little Ealls, where 

 the divide between the eastward-flowing Mo- 

 hawk and the westward-flowing Ontario River 

 was situated. At the Thousand Islands oc- 

 curred another divide, between the northeast- 

 ward-flowing preglaeial St. Lawrence and a 

 southwestward-flowing tributary of the On- 

 tario River. Spencer's Laurentian River, 

 which carried the drainage of all the Great 

 Lake valleys (except Superior) out across the 

 Thousand Island divide, never existed. There 

 is no good evidence for, and abundant evi- 

 dence against, its existence. 



To sum up : The evidence seems to be all 

 in favor of southward drainage in Tertiary 

 time of the streams which cut the Finger 

 Lakes and the other parallel valleys of New 

 York. Many of these were subsequently 

 deepened by ice erosion. Part of this drain- 

 age went out by the Susquehanna to the At- 

 lantic, and that of the more western valleys 

 probably to the Ohio and Mississippi embay- 

 ment. The drainage of the valleys of the 

 Great Lakes also went out in that direction, 

 and the system developed as a normal sequen- 

 tial drainage system on a peneplain surface of 

 nearly horizontal strata. Capture of the head- 

 waters of the New York streams left their 

 beheaded portions in the old valleys which 

 they had not the power to further deepen or 

 widen. The Ontario Valley, however, was 

 deepened without reference to the Einger Lake 

 Valleys. All this occurred while the land in 



the north stood higher than now, and the 

 Mississippi embayment and the Atlantic coast 

 south of New York, lower, as shown by 

 marine sediments of Tertiary age. 



A. W. Geabau 



Columbia Univeesitt, 

 December, 1907 



NOTES ON A SMALL COLLECTION OP SHELLS FROM 

 TEXAS 



During part of the month of August, 1906, 

 Mr. A. B. Wolcott, a Chicago entomologist, 

 collected extensively about the region of 

 Brownsville and Corpus Christi, Texas, and 

 incidentally secured an interesting collection 

 of land and fresh-water mollusks. Mr. Wol- 

 cott found the river very high and hence was 

 able to do nothing in the way of collecting 

 the Unionidse. A few fresh-water shells were 

 secured from the river drift. The land mol- 

 lusks were notably abundant, particularly the 

 Polygyras and the Bulimulse, as were also 

 the Helieinas and the Euglandinas. No 

 novelties were obtained, but the material 

 seems to be of enough interest to be placed on 

 record. The collection has been presented by 

 Mr. Wolcott to the Chicago Academy of Sci- 

 ences. 



In working up this list constant reference 

 has been made to the excellent paper by 

 Pilsbry and Ferriss, on the " Mollusca of the 

 Southwestern States," II., published in 1906 

 in the Proceedings of the Academy of Natural 

 Sciences of Philadelphia, page 134. 



HELICINID.a; 



Helieina oriiculata tropica " Jan " Pfr. 



Corpus Christi; tropical forests, Esperanza 

 ranch, Brownsville, on shrubbery; river drift, 

 Brownsville; on beach, Port Isabel. 



In a lot of 25 specimens, 5 are partly red. 

 and blue and the balance are blue. A common 

 species in this locality. 



HELICIDJE 



Praticolella griseola (Pfr.). 



Chaparral near Brownsville; old Fort Brown 

 and in river drift, Brownsville; Port Isabel, on 

 beach. 



The specimens collected show a wide range of 

 variation in the number and position of the 



