THE TANGANYIKA PROBLEM. 



2 55 



the walls of the body, and then bend down, uniting with 

 each other below the mouth. This connection appears, 

 therefore, to be unquestionably the labial commissure 

 described by Bouvier as characteristic of a number of the 

 Archi-tsenioglossate and Rhipidoglossate types. 



The cerebro pedal connectives are long, and altogether 

 the length of the cerebro-pleural, cerebro-pedal, and pleuro- 

 pedal connectives gives to the nervous system the longi- 

 commissurate character described by Haller. 



The pedal ganglia (Fig. 37) are united by a rather small 



Fig. 38.— The animal of Nassopsis nassa removed 

 from its shell to show the characters of the 

 operculum, op. 



connection, and are prolonged into the foot along the course 

 of two well-developed scalariform pedal cords. Between 

 these pedal cords there exist ladder-like connections 

 similar to those found between the pedal cords of 

 Cyclophorus. 



The otocysts in Nassopsis are relatively immense. They 

 are situated well up on the course of the pedo-pleural con- 

 nectives, and the otocyst nerves pass obliquely from them 

 towards the cerebral ganglia. The otoliths are small, 

 numerous, and rectangular, with the faces slightly convex. 



The reproductive apparatus in iVassopsis is somewhat 



