YII. — On the Modification of the Apex in Gastropod Mollusks. 



BY FEANK COLLINS BAKEE. 

 Kead April 5, 1897. 



Some time ago* the writer published some notes on the modi- 

 fication of the apex in Murex, and at the time these papers were 

 published a noted conchologist suggested to the writer that he 

 extend his observations to other groups ; the following notes are 

 the results of such suggestion. 



One of the greatest, if not the greatest, drawback to investiga- 

 tions of this kind is the paucity of perfect material. Every con- 

 chologist knows how difficult it is to secure specimens with a 

 perfect apex. In the collection from which these notes are 

 drawn, only about five per cent, of the specimens are available for 

 the notes embodied in these pages. I am not able to refer to any 

 publication in which similar investigations have been made, 

 although some species have the apex described in almost all re- 

 cent papers on the Mollusca, particularly those of Pilsbry, Dall, 

 Yerrill and Watson. I know of no paper dealing exclusively 

 with the form of the apex in gastropodous mollusks, save my 

 own mentioned above. If there are such, my ignorance of them 

 must be my excuse for not mentioning them. 



There appears to be primarily three types of apex, with num- 

 erous variations : (1) whorls numerous, carinated, nucleus promi- 

 nent ; (2) whorls numerous, rounded, smooth, nucleus prominent ; 

 (3) whorls few, rounded, nucleus buried in the coil of the second 

 whorl. The material examined is not numerous enough to 

 generalize upon at present, but that which has been examined 

 leads to the above conclusion. There are some 15,000 species of 

 gastropodous mollusks of which but a few hundred have been ex- 

 amined for the apex, so that much work must be done before con- 

 clusions can be made. In some groups the apex variation seems 



*Proc. Phil. Acad. Set., 1890, pp. 66-72 ; 1894, pp. 223-224 ; Eoch. Acad. 

 Set., 1891, p. 130-132. 



Annals N. Y. Acad. Sci., IX, Aug., 1897.— 45. 



