66 ZAPHYSEMA. 



appendix, which seems to be glandular, and terminates in two long 

 flagellum-like organs ; the retractor-muscle arises from a median 

 dilation of the penis. Vagina short, narrow ; uterus enormously 

 distended with young shells. Spermatheca globular, situated on a 

 very long duct, which is apparently branched (pi. 35, fig. 12, Z. tener- 

 rima). 



Jaw wide, arcuate, with a slight median projection ; composed of 

 narrow vertical flat plates soldered together, their outer imbricating 

 edges appearing as delicate spaced vertical strise ; above projects a 

 narrow conical process, springing from the middle of its surface (pi. 

 35, fig. 10, Z. tumida). 



Radula composed of short teeth with square basal-plates. Centrals 

 having the mesocone about as long as the basal-plate, and very 

 broad, side cusps small but well developed. Lateral teeth similar, 

 but lacking entocones. Marginal teeth low and wide, the mesocone 

 large, sometimes bifid at the apex ; ectocone simple or bifid (pi. 35, 

 fig. 11, Z. tenerrima', pi. 35, fig. 9, Z. tumida'). 



Distribution, Jamaica. 



The shell in this genus is globose, with large body-whorl, spire 

 convex or low-conoidal, lip sharp and thin. The jaw is like that of 

 Thysanophora and Sagda in structure, being of the stegognathous 

 type. The dentition closely resembles that of the two genera named, 

 but in Sagda the mesocones are longer. The foot in the three genera 

 Thysanophora, Sagda and Zaphysema is practically the same in 

 structure. The genital system is similar in general features to that 

 of Sagda. The modes of reproduction are identical in the three 

 groups. 



Binney has examined the jaw and teeth of Z. tumida; the writer 

 has figured the teeth and genitalia of Z. tenerrima. The other species 

 are still unknown anatomically. 



The group Cysticopsis, in which these forms have hitherto been 

 placed, differs widely from them in anatomical features. It must be 

 included in the genus Hemitrochus as a sectional division. 



In the single individual of Z. tenerrima examined, the thin- 

 walled uterus contained 27 young shells, and an egg, which was 

 globular, with thin brittle white shell. The young shells are 

 depressed-globular, translucent, often iridescent, and measure alt. 

 1'5, diam. 2 mill. ; whorls two. It would seem that in Thysanophora, 

 Sagda and Zaphysema eggs are normally formed, having the shell 

 .hard and calcareous. In some species of each group the eggs 



