COCHLITOMA. 77 



duction ovo-viviparous, the young shells at birth decidedly 

 larger than the eggs of Achatinae of corresponding adult size. 



Type Bulimus zebra Brug. Distribution, South Africa. 



The distribution of Cocklitoma is roughly limited on the 

 north by the Tropic of Capricorn. A few species of Achatina, 

 such as A. panthera and A. immacidata occur south of this 

 limit. 



Almost all of the South African Achatinse belong to 

 Cochlitoma, and agree in having the apex ratlier large and 

 rounded, the first whorl nearly flat, smooth except for slight 

 ripples, several following whorls decussate-granulose. This 

 sculpture may extend to and upon the last whorl. They are 

 ovo-viviparous, producing numerous young at a time. In 

 typical Achatina the apex is more trochiform. By accelera- 

 tion, the decussate sculpture, so characteristic of the stage 

 of maturity in Achatinida, has invaded the embryonic stage, 

 so that the first whorl only of the unborn young is smooth, 

 while Achatina proper is a much less evolved generic type, in 

 which several whorls of the protoconch are smooth. 



In the uterus of a specimen of A. zebra. Semper found about 

 60 undeveloped eggs with thick, calcareous shells, the smallest 

 3 mm., the largest 6 mm. long; then 25 embryos which had 

 crawled out of the egg-shell ; on the foot the embryos carried 

 a large podocyst, which in the youngest individuals enveloped 

 the whole shell of l 1 /^ whorls. See also under A. crawfordi, 

 species no. 18. It is likely that some species will be found 

 to be oviparous. 



Metachatina kraussi (Vol. XVI, p. 307) is so closely re- 

 lated to the present group that it is doubtful whether it should 

 be separated generically on account of the single character of 

 an obsolete columellar truncation. The form and sculpture 

 of the protoconch and the method of reproduction are identi- 

 cal in Metachatina and Cochlitoma. 



Cochlitoma was proposed by Ferussac to comprise snails 

 with the shell ovate or oblong-ovate and having the columella 

 truncate below, a group practically equivalent to Achatina 

 of Lamarck's Animaux sans Vertebres, and of most subse- 

 quent authors during more than half of the last century. 



