; >.\ s < "' 



i 



to side, at any rate they are much less sinuate in the middle than is the margin of 

 theaperturr 



The ventricose volutions, shallow sinus and broad transverse furrows (on caste) 

 are tin- -li-tiurtive features. Very young specimens may look much like the largest 

 <,f /'. } ,,-n:,lnt,i. luit the adult form, which is all we have seen, is certainly quite 

 distinct. /'. obesa should be compared with the British /'. bilobatu Sowcrby sp. (see 

 lig. ;5. p. sf'.) because it is, according to our opinion, the nearest known American 

 representative of that much (mis-) quoted species. And still the American form 

 is distinct if only for the reason that the apertural sinus is deeper in the bilobata. 



Formation and locality.- Lower beds of Ui. Tr.'nt<.ii k 'ruup. Bunfinand Danville, Kentucky. 

 CMHNM.-B.aUM*. 



Gemi* Ti: I i:\NOTA, n. gen. 



ftur>ini<i (pan .. II M i 1*47, Pal. Nt-w y..rk. vnl. I, p. 186. 



Brf 'AiimiKii.. 1-74. Gnl. Win., vol. Iv, p. 223. 



(part.), KOKKN, 1889, Nctu* Jahrbuch f. Mlneralotfle, etc , BellagebaiKl \i. p. 3. 



i generic characters see page M '.'. 



SuperHcially examined the systematic position of this genus will probably 

 appear to be between Megalomphala ami Kuphtmus. The relation to the latter how- 

 ever is more apparent than real. Comparing the five species now referred to 

 Tttninota we find that the umbilicus, though always present, is yet somewhat 

 variable, being very large in T. macnt, T. serrnrinntu and T. bidorsata, moderate in 

 T. obsolete, and 'comparatively small in T. irisconsintnsis. The vertical expansion of 

 the aperture is extremely limited in all save the last mentioned, and in this the 

 vertical diameter of the volutions also i? greatest. The external sculpture, aside 



i the revolving ridges, consists chiefly of lines of growth. These are always 

 regular and sharp, hut vary in strength with the species. 



While strong revolving lines like those of liucania or of Bucanopttisto not occur, 



nevertheless a fact that in all cases of Tetranotn preserving the external layer 

 of the shell, or an impression of the same, we observed a row of minute prominences 

 on each of the sublamelliform lines of growth. In a few instances we found further 

 that these prominences were in reality the anterior terminations of very fine short 

 >tru crossing from line to line. This style of sculpture, excepting that it is much 

 finer, is essentially the same as that marking the H. lindxleyi section of /';</(./. 

 We attach great weight to this point and believe that it proves our association of 

 the genus with the Huraniiiltr to be well fouml"l. 



The four revolving dorsal ridges, which we regard as the principal peculiarity 

 of the genus, are always distinctly developed on the inner volutions. In T. sejxar- 



