1899.] NATURAL SCIENCES OF PHILADELPHIA. 373 



Summary. — The two genera described above are not closely 

 related to forms known anatomically from other regions, and there- 

 fore throw no light upon the vexed questions of the alliance of the 

 South American fauna to that of tropical Africa or other regions. 

 They can have no bearing on the hypothetical Antarctica. Neo- 

 belisciis is the most highly specialized member of the Achatinidce 

 known, and apparently forms no ca^isule of albumen, but nourishes 

 the embryo directly, as in mammals. The teeth are ultra-achati- 

 uoid, and the muscJe system aberrant. Callionepioii is probably an 

 individualized survivor of a primitive achatinoid, retaining the 

 early form of teeth. There is no reason for believing that either 

 genus reached South America from without. 



DESCRIPTION OF PLATES. 

 Plate XV. 



Fig. 1. Neobeliscus calcareus (Born). Teeth of an adult indi- 

 vidual. R., rachidian or median tooth; the side teeth 

 are numbered. 



Fig. 2. Teeth of a uterine young individual (fig. 7) of the same 

 species. 



Fig. 3. Callionepion Iheringi n. sp. Teeth. R., rachidian; L., 

 1 ; laterals 15, a marginal tooth. 



Fig. 4. Neobeliscus calcareus. Jaw. 



Fig. 5. Neobeliscus calcareus. Genitalia of an individual carry- 

 ing two uterine young, the anterior one about at full 

 term. X IJ. No. 73,455, coll. Acad. Nat. Sci. Phila. 

 a. gl., albumen gland; atr., atrium; h. d., hermaphro- 

 dite, or ovisperm duct; r. r., right retractor muscle; 

 ]). r., penis retractor; jj., penis; sj)., spermatheca; t , 

 talon; td., uterus. 



Fig. 5«. Albumen gland (a. gl.), talon (t.) and beginning of the 

 hermaphrodite duct (A. d.), of the same individual. 

 X 4, the organs separated. 



Fig. 6. Uterine young of the same, ventral aspect. /., foot; ap., 

 placenta- like appendage. Somewhat less than natural 

 size. 



Fig. 7. Shell of the same. Somewhat less than natural size. 



