CERION. 177 



9th tooth, and a short outer cusp. The marginal teeth are short and 

 wide, with two cusps (pi. 47, fig. 35, C.incanum; fig. 36, O. columna, 

 both after Binney). 



In C. regium, incanum and chrysalis, the basal plate of the central 

 tooth is as short as the middle cusp ; in C. abacoense and C. columna 

 it is longer. 



Semper (Reisen im Phil. Archip., p. 128) says that O. uva has 95 

 to 99 teetli in a row, all the teeth with several cusps. This is a 

 third more teeth in a row than the other species examined, which 

 have 55 to 60. 



The jaw (pi. 47, fig. 29, O. m. chrysalis) is rather strongly arcu- 

 ate, solid, smooth, with a small median projection below. This pro- 

 jection is said to be wanting in C. uva, but is present in other species 

 examined. 



Free muscles (pi. 47, fig. 28, C. m. chrysalis). The left tentacu- 

 lar and ocular retractor and the pharyngeal retractor are free almost 

 throughout, being united with the columellar muscle at its proximal 

 end only. The right tentacular and ocular retractor is united with 

 the columellar muscle for a short distance, and distally it gives off a 

 broad muscular band inserted on the vagina, functioning as a vagi- 

 nal retractor. The eye retracts between the branches of the geni- 

 talia, as usual. 



The genital system (pi. 47, fig. 34, C. m. chrysalis) is of normal 

 general proportions and position. The atrium is very capacious and 

 contains a short, tongue-shaped fleshy appendage. The penis is 

 stout below, tapering rapidly, with a long slender retractor muscle 

 arising at its apex and inserted upon the lung- floor. Its inner walls 

 are coarsely plicate longitudinally. Below the middle of the penis 

 the epiphallus is inserted, entering between two fleshy lips. The 

 epiphallus is glossy, moderately swollen, and passes into an exceed- 

 ingly long, compactly coiled vas deferens (seen partially pulled out 

 in the figure). The vagina is much shorter than the free oviduct. 

 The spermatheca is oblong, on a long duct, which branches into a 

 very long diverticulum, lying against the uterus (but pulled free in 

 the figure). There is a strong vaginal retractor, given off from the 

 right tentacular band, apparently a diverted anterior pedal retractor. 



In copulation the atrium and penis are everted (pi. 47, figs. 32, 

 33), the former forming a sort of hood over the latter. 



In C. m. chrysalis the spermatheca and duct are 19 mill, long, 

 and the diverticulum 18 mill. 



