194 J. E. S. MOORE. 



of teeth beiTig represented in PL 21, fig. 9. The outer and 

 inner lateral teeth distinctly resemble those of the Melano- 

 planaxoid type which I ^ described in considering the relation- 

 ships of the genus Tanganyikia, and are something similar to 

 those of the " Neomelanian^' group of the brothers Saracin;** 

 while the admedian tooth is peculiar, owing to the presence of 

 two small subsidiary denticles on the inner face (PI. 21, fig. 9), a 

 very peculiar feature, and one which is only exemplified in the 

 radula of Tympanotamus. The presence of this peculiarity, 

 together with the general character of the radula, should cer- 

 tainly be regarded as of weight in diagnosing the nearer affini- 

 ties of this form. And, as we shall see in placing it along 

 with Tympanotamus, it is certainly in accord with the rest 

 of the animal's morphological peculiarities. 



The oesophagus and salivary glands (PI. 21, fig. 7, s. g.) are 

 in all ways similar to those of Ty phobia, but these characters 

 are common to so many diff'erent kinds of Gastropods that they 

 are of little value from a special morphological point of view. 



The stomach has two chambers, the anterior of which (PI. 

 21, fig. 13) contains a style. The intestine is simple, and takes 

 the course represented in PI. 21, fig. 13. The rectum is not 

 dilated, nor beset with any accessory gland. The bile-ducts 

 seem to open by two very small apertures upon the base of the 

 posterior stomachic chamber. Stomachic valves are feebly if at 

 all developed. The liver is large, and occupies much the same 

 position as in Nassopsis (loc. cit.). The excretory organ 

 occupies a place in front of and above the heart, and opens by a 

 minute pore at the extreme upper end of the mantle cavity 

 (PI. 21, figs. 5 and 13, r.«.). 



The heart has the usual teenioglossate characters, consisting 

 of an auricle, ventricle, and aortic trunk ; but the last struc- 

 ture is much less developed in Bythoceras than in many 

 forms, — as, for example, in the genus Ty phobia.^ 



• Loc. cit. 



' " Die Siisswasser-MoUusken von Celebes " (Wiesbaden, C. W. Kreidel's 

 'Verlag'), 1898. 

 » Loc. cit., ' Quart. Joum. Micr. Sci.,' vol. 41, 1898, p. 190. 



