THE NADTILUS. 33 



G. intersita Halfl. G. infantula Lea. 



G. suturalis Hald. G. louisvillensis Lea.' 



G. costifera Hald. G. pulcliella Antli. 



G. cubicoides Anth. G. gracilior Anth. 



G. spartenburgensis Lea. G. translucens Anth. 



G. iota Anth.' G. interlineata Anth. 



G. tecta Anth. G. ohioensis Lea. 



G. gibbosa Lea." G. brevispira Anth. 



G. depygis Say. G. semicarinata Say. 



G. livescens' Menke. G. haldemani Tryon. 



G. milesii Lea. G. informis Lea.* 



G. lithasioides Lea. G. virginica Gmel. 



The specific value of some of the above is doubtful, and to settle 

 points in question will require large series of specimens, preferably 

 from the localities where the types were found. I would suggest that 

 any one who can do so, collect such a sei'ies, including all stages of 

 growth, make a note of the situation where found, and send the same 

 to Mr. Billups, if he decides to go ahead with the work. 



I am sure some new species will be found, but I hope no specimens 

 will be described as new until their validity is well established. 



If tlie different groups of the Strepomatido'. could be studied as 

 thoroughly as lo has been by Mr. Chas. C. Adams, a large share of 

 the doubtful species could be eliminated. There are other species 

 which show nearly as great a variation as the lo; for inst^ince, Pleu- 

 rocera canalieulatum Say has a wide variation in form and varies 

 from a smooth surface to one with two well-developed grooves on the 

 body-whorl. Angitrema arrnigera Say is also quite variable in both 

 form and tubercles, some specimens having a row of double tubercles 

 on the periphery of the body whorl. I am strongly of the opinion 

 that the specimens described by Dr. Lea as Meseschiza grosvenorii 

 were young Ang. armigera Say; his description and figure fits many 

 of the young of that species, excepting for the notch, which is prob- 

 ably abnormal, as Tryon held. Angitrema duttoninna Lea and Lith- 

 asid dow7iiei Lea may only be variations of Ang: armigera Say ; 

 specimens I have collected in Tennessee seem to indicate it. 



1 Ohio? see Amer. Jour, of Conchology. 



^Described from two specimens and said to be a " remarkable species." 



' Described from two imperfect specimens. 



* Described from two specimens. 



