102 OXYSTYLA. 



Shell imperforate, ovate-conic, usually rather thin but strong, com- 

 posed of 5 to 8-J- moderately or slightly convex whorls ; apex obtuse, 

 the earlier 2 or 3 whorls smooth; aperture ovate, oblique, rounded be- 

 low, the Up simple and unexpanded; columella slender, straight or with 

 a moderately convex fold, not truncated at base. Coloration usually 

 of longitudinal, waved or zigzag stripes, more or less modified by three 

 equidistant spiral bands. 



Type Bulimus undatus Brug. Distribution, tropical and sub-tropi- 

 cal America. 



Genitalia without accessories except a small lobed gland upon the 

 penis, rarely obsolete. Teeth usually with rounded cusps, but those 

 of the median teeth are rarely pointed, and in some species, such as 

 0. princeps, the cusps vary in different individuals from long and 

 lance-shaped to short and obtuse. 



The fundamental color pattern is a combination of three bands at 

 equal distances on the last whorl, with longitudinal stripes, the bands 

 being probably the more fundamental and older element. These 

 bands are apparently the remnant of an original five-banded pattern, 

 such as may be seen in various forms of Drymceus ; and following 

 the usual notation, a banded Oxystyla has the band formula 02340. 

 In some species and races, such as 0. melanocheilus, tricinctvs,flori- 

 densis, this pattern stands alone ; in others, such as reses, ferussaci 

 deceptor, it is found in combination with stripes ; while in the striped 

 forms without distinct bands, their position is indicated by a sinua- 

 tion, angle or spot in the stripes, showing the fundamental impress 

 of the tendency to trifasciation in the organization of the animal. 

 Striped species seem to have a tendency to revert to the trifasciate 

 condition; and the full recognition of the several ," melanocheilus " 

 forms (pi. 18) occurring in Mexico, Central and South America, and 

 Florida, as parallel modifications of several flammulate specific or 

 varietal stocks, arid wholly independent of each other, is the main 

 contribution I would make to the body of general ideas bearing on 

 the study of species and races. In a few forms, such as 0. longa, the 

 bands seem wholly lost, the stripes being straight. In 0. zonifera 

 there is a tripartite division in the general color tone of the shell. 



VARICES, as the black or dark streaks reminiscent of former peri- 

 stomes or lt resting periods " may be called, are doubtless directly 

 due to climate ; their number and spacing depending upon the two 

 factors of rate of growth of the individual, and frequency or rarity of 



