THE NAUTILUS. 107 



tion and the Sonoran area in Texas, there is along its border an ap- 

 parent, rather than a real, intermingling of the fauna, owing to the 

 fact that the eastern species follow up along the river valleys, while 

 at the same time " the fauna on the bluffs or away from the streams 

 is frankly Sonoran." The scope of the present paper is, in the 

 main, restricted to the species of the Sonoran region, only such of 

 the Austroriparian species are mentioned as were actually collected 

 by the authors. 



The list of the forms considered characteristic of the Sonoran 

 region in Texas includes twenty-one genera and thirty specie.-. Of 

 the former, nine are not known to occur in the Austroriparian or 

 humid region of Texas. And of the latter, nine species and varieties 

 are described as new. The larger and more important part of the 

 paper is taken up with a monographic revision of the Texan Buli- 

 iiuiU, which have so long been a source of exasperation and despair 

 to the American collector. It appears that the typical forms of B. 

 alternatus and schiedeanus do not, so far as known, occur in the 

 United States. The Texan series is restricted to B. dealbatus and 

 B. alternatus marise. The specific distinction of dealbatus and 

 alternatus is clearly established by the details of the genitalia. The 

 typical form of dealbatus ranges from Alabama and Kentucky west to 

 Kansas. West of the Mississippi from southwestern Missouri 

 through Arkansas and the Indian Territory to Texas a number of 

 well characterized local races have been differentiated, of which six 

 are recognized and fully described and figured. B. alternatus mariee 

 ranges through a wide territory along the Rio Grande from the Gulf 

 as far west as the Pecos river. Its exact western range has not been 

 determined. While there are some general differences between the 

 eastern (typical) and western forms, the intergradation is so com- 

 plete that the authors do not deem it advisable to attempt to separate 

 them into the distinct races. 



Another important part of the paper is a revision of the genus 

 Helicodiscus, of which four species and one variety are recognized. 

 It is something of a shock, like that of losing an old friend, to learn 

 that lineatus of Say must be given up, but fortunately it is replaced 

 by another name, parallelus, of the same author. 



Other corrections in nomenclature to he noted are, that Helix sayi 

 of Binney was preoccupied by Wood tor an uncertain species of 

 Polygyra, hut probably auriform is ; and our well-known eastern 



