THE NAUTILUS. 



STBOBILOPS replaces STROBILA, then STROBILOPSIDJE must replace 

 STROBILID.E according to the rules of priority and synonymy. ) 



The following description applies only to S. labyrinthica. 

 How closely the other species come to this, and the amount of 

 variation in the group, can only be ascertained by more ex- 

 tended anatomical investigation. 



Animal without pedal grooves or caudal mucous pore but 

 having a network of incised lines on the surface of the skin. 

 The meshes of this are quite large. Tentacles and eyestalks, 

 normal. Genital opening just back of the right eyestalk. Fore 

 part of the body, black: tail region light gray and sole of foot 

 white. 



Kidney, long and slender, very little larger than the duct, the 

 ureter, which leads directly therefrom to the mantle margin. 

 The duct is separated from the rectum by a distance equal to 

 the diameter of the latter. It appears to discharge immediately 

 above the breathing pore. 



The genitalia are characterized by the excessively long fla- 

 gellum on the penis. One branch of the bifurcated retractor 

 muscle is attached at the junction of the penis and flagellum: 

 the other is attached to a bend of the vas deferens a short dis- 

 tance above its union with the penis. The distal end is at- 

 tached to the right optic retractor muscle. The vas deferens is 

 considerably swollen in the section nearest the penis. Here it 

 is almost as large as the latter organ. It gradually becomes 

 smaller however and discharges high up on the oviduct. The 

 appendix is swollen in its distal end to the diameter of the penia 

 and it has there an abrupt flexure. Whether this is due to the 

 retraction of the organs and therefore accidental or whether it is 

 natural, has not been ascertained. The penis and vagina unite 

 at the point of exit. There is no appreciable atrium or cloaca. 



The vagina is a thin-walled, slightly pouched organ, smaller 

 in diameter at its junction with the penis than elsewhere. The 

 upper end corresponds to what is usually called the oviduct in 

 land snails, but there is not a point of demarcation between the 

 two in this species. The upper end is folded into a series of 

 lamellar pouches, all of which fit close together like plates. 

 The walls in this region appear to contain some glandular tissue. 



