NATURAL SCIENCES OF PHILADELPHIA. 157 



since been detected in Gl. truncata* rosea,' 2 algira, 3 Sowerbyanaf 

 plicatulaf fusiformisf Albersi ; 7 in semitarum, 8 Phillipsi 9 of the 

 subgenus Varicella; also solid u la 10 of subgenus Oleacina. This 

 central tooth is rather difficult to study, being on a different plane 

 than the other teeth, and apparently much less developed. Its 

 cusp is generally simple, long, and narrow ; but in G. rosea it has 

 a decided blunt cutting point, and in G. semitarum it has a long, 

 slender, cutting point. 



The side teeth are all of the purely aculeate type ; the base of 

 attachment is long, narrow, incurved at sides, gradually rounded 

 above, expanded and bluntly truncated below, the general out- 

 line being somewhat like that of the sole of a shoe. From this 

 base of attachment springs a large aculeate cusp. These side 

 teeth are like the marginals in Zonites, Limax, etc.; they may 

 therefore be called marginal teeth, and the lateral teeth, usually 

 present in the Vitrininee, may be said to be entirely wanting. 



As stated above, the marginal teeth increase rapidly in size for 

 a short distance from the median line, and then gradually de- 

 crease in size, as they pass off laterally, the last tooth being still 

 smaller than the first. 



Glandina truncata has 32 1 32 teeth in each row. I have 

 shown in plate I., fig. la, the central and first three marginals ; 

 b is the twentieth marginal ; c, the last tooth. Fig. a and c show 

 the teeth as seen from below, thus giving a perfect view of the 

 bases of attachment. Fig. b is a strictly profile view. The eighth 

 tooth seems to be the largest. The central tooth I find great dif- 

 ficulty in studying. It appears to have a simple, long, slender 

 base of attachment, truncated above and below with slightly ex- 

 panded lateral angles. The sides are somewhat incurved, giving 

 the tooth the appearance of a simple modification of the base of 

 attachment of the marginals. The figure (2) by Morse, copied 



' See L. and Prw. Shells, I., fig. 6. 



2 Amer. Journ. Conch., V. 202, fig. 1. 



3 Fischer and Crosse, J. de C. XVI. 234, 1868 ; Moll. Mex. et Guat., pi. 

 IV. fig. 10. 



* Same, Moll. Mex. et Guat. 73, pi. IV. figs. 6-9. 



6 Same, p. 73. s Same, p. 73. 



7 L. and Frw. Shells, I., fig. 10, p. 19. 



Proc. A. N. S. Phil. 1874, 49. 8 Same. 



"> Ann. Lye. N. H. of N. Y., X. 347. 



