68 



ZONITIDAE 



MESOMPHIX PERLAEVIS VULGATUS H. B. Baker 



The shell of Mesornphix perlaevis vulgatus is likely to be 

 confused with shells of Mesornphix cupreus and Mesornphix 

 friabilis. It differs from them in the following particulars. The 



shell is smaller and measures less 

 than an inch (20 mm.) in diame- 

 ter; the body whorl is of relatively 

 less height; and the aperture, con- 

 siderably wider than high, is more 

 transversely elliptical than those ni 

 cupreus or friabilis. The base is 

 smooth and shining; the upper sur- 

 face is very finely ribstriate; the umbilicus is almost closed. This 

 shell, of a satin-finish luster, is brown above and greenish or 

 yellowish below. A wide white callus borders the edge of the 

 lip. Mesornphix perlaevis perlaevis is not found in Illinois. 



The body and foot of the animal are pearly white ; the head 

 and eye peduncles are dark blue. 



The variety Mesornphix perlaevis vulgatus is common to 

 abundant in the hill region of southern Illinois and on the bluffs 

 of the Ohio River. It prefers forests of oak, elm and hickory, 

 with bushes of hawthorn, hazel, gooseberry and sassafras, and 

 vines such as Virginia creeper and poison ivy. It is found under 

 logs and among forest debris. In some of the smaller valleys it 

 can be found under large blocks of stone in gullies, where it has 

 sought concealment and moisture. It is at present known in 

 Illinois only from the counties of Saline, Gallatin, Pope and 

 Hardin. 



This species was long known under the name Zonites laevi- 

 gata, a figure of which was published in Ferussac's Natural 

 History of Mollusks. Special inquiries carried on by Dr. H. B. 

 Baker revealed the fact that Ferussac had never described this 

 shell, but had mistakenly attributed the authorship of the name 

 to the eccentric French naturalist Rafinesque. Zonites laevigata 

 thus becomes what is known as a nude name, not described by 

 anyone. Dr. H. B. Baker in 1933 applied this name to a race 

 of the species perlaevis. A complete revision of the shells form- 

 erly classified under the name laevigata has been made by Dr. 

 H. B. Baker in his Check List of Nearctic Zonitidae, published 

 in 1933. 



