1889.] NATURAL SCIENCES OF PHILADELPHIA. 137 



sections of the genus Astralium. This process is followed by the 

 obsolescence of the inner lateral teeth, shown in certain species of 

 Astralium in which the cusps of these teeth are absent. The same 

 course had been followed in the Neritopsidse, where, as Dr. Fischer 

 has shown, the central and inner lateral teeth have been lost. 

 Attention was called to the anomalous radula of Phasianella uirgo 

 Angas, a species of Orthomesus in which the rhachidian tooth was 

 replaced by a false central tooth, formed by the coalescence of the 

 two inner lateral teeth. 



Remarks on Oliva inflata, Chem., 0. irisans, Lam. and other 

 species of shells. — Mr. John Ford exhibited a large number of 

 specimens representing Oliva inflata Chem. and Oliva irisans Lam. 

 In referring to the various colors and forms of the series shown he 

 called attention to the difficulties attendant upon a correct separa- 

 tion of the species comprised in the genus. As evidence of 

 thereof it may be said that fully one hundred and fifty names 

 have been applied to the species which altogether do not number 

 more than sixty. 



Mr. Tryon reduced the number to fifty-five, and a careful 

 examination of the Academy's collection will show no reason for 

 questioning his judgment. 



Very many of the discarded names were, by Marratt and other 

 writers, avowedly based upon color varieties only. A larger number, 

 however, may be safely charged to the lack of opportunity for 

 comparing the newly-discovered specimens with others already 

 named, and an absence of the literature referring to them. 



These latter difficulties can be readily comprehended if a casual 

 glance be given to the two species under consideration, showing as 

 they do at least twenty varieties of color, including one perfect 

 albino, and half as many different forms. And yet a close observa- 

 tion will satisfy the most skeptical student that certain characters 

 proving their specific distinction are present in each. 



These conclusions apply also to several other species belonging to 

 the genus,- — markedly so to 0. ispidu la Lam. 0. amneosa Lam., and 

 0. reticularis Lam., — each shell in the first-named species varying in 

 color, and often in form, from either of its otherwise closely allied 

 fellows. 



While much that has been said will apply with equal force to 0. 

 irisans, it has been deemed best in this instance to retain several of 

 the names formerly held as specific, but with the understanding that 

 they be used for varieties only. 



Thus we have as the type of the species, 0. irisans, Lam., and as 

 varieties, concinna Marratt, tremulina Lam., erythrostoma Lam. 

 and textilina Lam. 



With the series of 0. inflata shown, there are a dozen specimens 

 belonging to the species, but which are distinct in two characters 

 at least from all of the others. To these the varietal name Ovum- 

 ralli, has been given by the speaker. Though all of the specimens 



