ANATOMY OF AMASTRIMS. 61 



Family AMASTEID^ Pilsbry. 



Amastrida PILS., Manual of Conch., xx, p. viii, 1910. 

 Amastrincs PILS., vol. xxi, p. xx. 



Orthurethra similar to Achatincllid(r, Tornatellinidcc and 

 Ferussacidce in pallial organs. Reproductive organs as in 

 Achatinellidtr except that the penial retractor muscle is sim- 

 ple, inserted on the penis at the base of the appendix. The 

 appendix is conspicuously enlarged distally ; the albumen 

 gland is well developed, and the duct of the spennatheca is 

 short. 



Jaw well developed, vertically striate, plaited or ribbed. 

 Radula oblong, distinctly divided into central, lateral and 

 marginal areas by differences in shape of the teeth, as usual 

 in land snails. Teeth in approximately straight, transverse 

 rows; centrals narrower than the laterals, with one or three 

 cusps ; laterals bicuspid, the basal plate quadrate ; marginals 

 having the cusps more or less split. 



Shell varying from discoidal and openly umbilicate to 

 ovate, turrited or subcylindric, with the axis umbilicate, per- 

 forate or imperforate ; usually having a columellar lamella 

 in the last whorl, but never a parietal lamella or palatal 

 plicae. 



Animal externally similar to Achatinellidcr, etc. External 

 genital opening is nearer to the mantle than to the eye 

 peduncle. Oviparous or viviparous. Mainly living on the 

 ground, sometimes (the genus Laminella) on plants. 



The differences in teeth, jaw and reproductive organs are 

 certainly sufficient to distinguish this group as a family dis- 

 tinct from the AchatinelUdce. Having found constant differ- 

 ences in several unrelated organs, in a large number of species 

 dissected, I have reconsidered my former opinion (vol. XXI, 

 p. xx ) that the Amastroid genera form a subfamily of the 

 AchatinelUda. The differences are far more fundamental 

 than those separating many families of mollusks, and there 

 seem to be no forms whatever, among the many which have 

 been dissected, which are in any way transitional. The shells 

 are much more alike than the soft parts, and this external 



